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NBS TECHNICAL NOTE 896

U.S. DEPARTMENT OF COMMERCE/ National Bureau of Standards

NBS Reactor:

Summary of Activities

July 1974 to June 1975
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards? was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology

and facilitate their effective application for public benefit. To this end, the Bureau conducts

research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology,

the Institute for Computer Sciences and Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United

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and commerce. The Institute consists of the Office of Measurement Services, the Office of Radiation Measurement and the following Center and divisions:

Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics — Center

for Radiation Research: Nuclear Sciences; Applied Radiation — Laboratory Astrophysics

" — Cryogenics 2 — Electromagnetics " — Time and Frequency 2

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materials needed by industry, commerce, educational institutions, and Government; provides

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Analytical Chemistry — Polymers — Metallurgy — Inorganic Materials — Reactor

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THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and

accessibility of scientific information generated within NBS and other agencies of the Federal Government; promotes the development of the National Standard Reference Data System and

a system of information analysis centers dealing with the broader aspects of the National Measurement System; provides appropriate services to ensure that the NBS staff has optimum

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1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.

- Located at Boulder, Colorado 80302.
NBS Reactor: Summary of Activities

July 1974 to June 1975

' ^JtoJ^fyKtoJL -Jfte&Li

Robert S. Carter

Reactor Radiation Division

Institute for Materials Research

National Bureau of Standards

Washington, D.C. 20234

°f£Au of

U.S. DEPARTMENT OF COMMERCE, Rogers C. B. Morton, Secretary

James A. Baker, III, Under Secretary

Dr. Betsy Ancker-Johnsan, Assistant Secretary for Science and Technology

V NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

It*

Issued January 1976
National Bureau of Standards Technical Note 896

Nat. Bur. Stand. (U.S.), Tech. Note 896, 150 pages (Jan. 1976) CODEN: NBTNAE

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1976

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington. D.C. 20402 (Order by SD Catalog No. C13.46:896). Price $2.15 (Add 25 percent additional for other than U.S. mailing).
FOREWORD

The National Bureau of Standards Reactor was built not only to serve the needs of the NBS but also those of the greater Washington

Scientific Community and other government agencies. The Reactor Radiation Division was established to operate the reactor and to foster its

scientific and technological use. Toward this end, the Division has a small nucleus of scientists experienced in the use of reactors for a wide range of scientific and technical problems. In addition to pursuing

their own research and developing sophisticated experimental facilities,

they actively seek out and encourage collaboration with other scientists,

engaged in challenging programs, whose work can benefit from use of the

reactor, but who as yet do not have the reactor experience necessary to

take full advantage of the facilities available. The Division also

provides irradiation services to a wide variety of users as well as engineering and other technical services.

The reactor operates at 10 MW and is designed to provide a broad

spectrum of facilities ranging from intense neutron beams to extensive

irradiation facilities, making it one of the most versatile high flux

research reactors in the country. Thus it is able to serve a large

number of scientists and engineers in a broad range of activities both

within and outside the NBS.

This report attempts to summarize all the work done which is dependent on the reactor including a large number of programs outside the

Division. The first section summarizes those programs based primarily

on Reactor Radiation Division (RRD) initiatives whereas the second and

third sections summarize collaborative programs between RRD scientists

and other NBS or non-NBS scientists respectively. The fourth section

summarizes NBS work originating entirely outside the RRD which requires

no collaboration with RRD scientists. The section entitled, "Service

Programs" covers those programs originating outside NBS but for which

RRD provides irradiation services. The remaining sections are selfexplanatory.

iii
ABSTRACT

This report summarizes all those programs which depend on the NBS

reactor. It covers the period from July 1974 through June 1975. The

programs range from the use of neutron beams to study of the structure

and dynamics of materials through nuclear physics and neutron standards

to sample irradiations for activation analysis, isotope production and

radiation effects studies.

Key words: Activation analysis; crystal structure; diffraction;

isotopes; molecular dynamics; neutron; nuclear reactor;

radiation.

xv
TABLE OF CONTENTS

Page

FOREWORD iii

ABSTRACT IV

A. REACTOR RADIATION DIVISION PROGRAMS 1 Neutron Scattering Studies of Hydrogen in Metals i

1. The Lattice Dynamics of PdD_ , „ i U. 6

3

x

2. The Acoustic Modes of the Phonon Dispersion Relation of

NbD 9

3. The Diffusion of Hydrogen in Polycrystalline

Thorium 5

4. Lattice Dynamics of Vanadium Deuteride 6 Crystal Dynamics, Phase Transitions and Orientational

Disorder in Ionic Crystals 6

1. Alkali Cyanides 6

2. Ammonium Iodide (ND.I) 9 4

Symmetry Analyses of Neutron Scattering in Crystals - Application of Time Reversal Symmetry 15

Theoretical Analysis of Phonon Decay Widths in KCN, NaCN. . 17

The Use of Position Sensitive Detectors in Single Crystal

Dif fractometers 17

Thermal Neutron Flux Measurements 21

Neutron Radiography 22

Gauge Theories 28

B. RRD-NBS COLLABORATIVE PROGRAMS- • 31

Total Profile Analysis in Neutron Powder Dif f ractometry . . 31

Conformation of Polymers in Dilute Solution 33

Hydrogen Bonded Dimers in SnHPO, 34

C. INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS 36

Crystal Structure of 1, 3, 5-Triaceto-2 , 4 , 6-Hexahydro-STriazizine (TRAT) 36

The Crystal Structure of Monovalent Metal Azides 39

Quasielastic Neutron Scattering Study of Ammonium-Ion

Reorientations in Ammonium Perchlorate 42

Polarized Raman Study of Ammonium Perchlorate 44

v
TABLE OF CONTENTS

Page

Low Temperature Phase Stability of Ammonium Nitrate - Potassium Nitrate Solid Solutions 46

Mode Gruneisen Parameters of KBr Determined byInelastic Neutron Scattering 47

Hydrogen Embrittlement in Titanium 48

Critical and Low Temperature Neutron Scattering From

Amorphous Magnets 49

Spin Waves in Amorphous TbFe„, 50

Anomalous Curie Temperatures of RFe_ Amorphous Materials 52

Neutron Diffraction Studies on Transition-Metal

Substituted Fe Si 54

Neutron Diffraction Studies of Biological Materials. . . 54

Mossbauer Studies on Dysprosium-Scandium and Amorphous

DyFe 55

Small Angle Scattering 59

A Diffraction Study of Amorphous Materials 61

Application of Robust/Resistant Techniques to Crystal

Structure Refinement 63

BT-4 Three Axis Neutron Spectrometer 65

A High Pressure System for Neutron Diffraction 67

D. NON-RRD NBS PROGRAMS 68

Activation Analysis: Summary of 1975 Activities .... 68

1. Basic Research in Nuclear Analytical Chemistry . . 69

2. Analytical Research Applied to Specific NBS

Programs 85

3. Analytical Support for the SRM Program 97

4. Service Analysis 97

Neutron Reaction Rates and Standard Neutron Fields ... 98

1. Mass Assay of NBS Fissionable Deposits 101

2. The NBS Double Fission Ionization Chamber 102

3. Absolute Fission Rate Measurements in CFRMF. . . . 104

4. Thermal Fission Yields for Long Lived Fission

Products 105

5. International Comparison of Absolute Fission Rate

1 Oft Measurement Scales

VI
TABLE OF CONTENTS

Page

6. Fission Cross Sections for Californium 252

Fission Neutrons 110

ft 1 Angular Anisotropy in the Li(n,a) H Reaction at 25 keV . . 113

Precision Measurement of the Wavelength of Nuclear Gamma

Lines and the Compton Wavelength of the Electron. . . H4

Measurement of the Ratio of the Absorption Cross Sections

for Manganese and Hydrogen H5

E. SUMMARY OF REACTOR OPERATIONS 118

Replacement of the NBSR Main Heat Exchanger 119

F. SERVICE PROGRAMS m

Activation Analysis Program of the Food and Drug

Administration at the NBSR 121

ATF's Forensic Activation Analysis Program 126

The Use of Activation Analysis in Scientific Crime

Detection by the Federal Bureau of Investigation • • 127

Lunar Sample Analysis for 17 Trace Elements 127

Trace Elements in the Environment and Radioactive Decay

Studies 128

Trace Elements in Oceanic Floor Rocks 129

Chemical Characterization of Marine Aerosols 130

Trace Element Studies of Selected Biological Specimen . . . 131

Activation Analysis Program of the U.S. Geological Survey 132

G. STAFF ROSTER 133

H. PUBLICATIONS i37

Vll

A. Reactor Radiation Division Programs

NEUTRON SCATTERING STUDIES OF HYDROGEN IN METALS

Our program to study the binding and diffusion of hydrogen in bcc

and fee metals in collaboration with scientists from Oak Ridge and

Argonne National Laboratories has continued. New results have been

obtained for the lattice dynamics of NbD and VD and for the diffusion

x x of hydrogen in ThH^. In addition, further analysis of the results for

the lattice dynamics of PdD have led to increased understanding of

many of the phenomena observed in this alloy system. The results

obtained from this work will be used to extend the program to other

metal hydrides and to help derive new models for the behavior of this

important class of non-stoichiometric interstitial alloys.

1. The Lattice Dynamics of PdD - J. M. Rowe and J. J. Rush

U • 0-/ In a continuation of our collaboration with H. G. Smith and Mark

Mostoller at ORNL and H. E. Flotow at ANL, we have completed our measurements and analysis of the lattice dynamics of RdD n ,_. We have used a Born-von Kafman model for this system to produce the density of states

g(w) shown in figure 1. In this figure, the dashed line represents

the predicted spectrum for PdH ,„ assuming no force constant changes . These frequency distributions and related integrals (e.g. the mean

frequency weighted by atom type) have been used by various groups to

explain other data. For example Papaconstantapolous and Klein (NRL)

have used the properly weighted mean square frequency in conjunction with

their electronic band structure calculations to derive the parameters

determining the superconducting transition temperature. The comparisons

with experimental data have already led to a new understanding of

superconductivity in this system. Also, M. H. Mueller and J. Faber

(ANL) have used the mean square displacements derived from our data to

show the existence of static displacements in their single crystal
REACTOR RADIATION DIVISION PROGRAMS

samples of PdD and PdH . x x Finally, in what is perhaps the most exciting and stimulating

development, A. Rahman (ANL) has used the parameters derived from our data to initiate a series of calculations on high concentration defect

systems. These calculations are both a test of the validity of our own fitting and analysis routines and an advance in the more general problem

of the effect of vacancies on crystal dynamics. The results show that

our admittedly arbitrary procedure for handling the lack of stoichiometry

in our sample gives surprisingly good results for derived properties (a

point of great importance to the applications discussed above) . Also

the calculations show that much of the discrepancy between our results

and earlier polycrystal spectra can be understood in terms of the non- stoichiometry . In order to fully exploit this new development, further

experiments will be undertaken to test the detailed predictions of the

function of the one7phonon cross-section, as a function of momentum

transfer. This represents the first experimental and theoretical study

of the effects of vacancies on the lattice dynamics of solids.

Finally, we are still attempting to produce higher concentration

samples of PdD . We hope to achieve values of x larger than 0.9 (which

will provide a T >4 K) so that we can determine the behavior of a high

c T sample. We are also extending this program to studies of Pd M

D where M=Ag, Cu. Such alloys have Tc's as high as 18 K and are of

great current interest. Progress in this area is dependent upon availability

of adequate single crystal samples.

2. The Acoustic Modes of the Phonon Dispersion Relation of NbD - x

J. M. Rowe, J. J. Rush and N. Vagelatos

We have completed our measurements of the acoustic modes of the

phonon dispersion relation in Nb, Nbd , and NbD , at 473K. The

results of these measurements have been analyzed in terms of Born-von

Karman models in order to derive approximate frequency distributions to

aid in comparisons of the overall features. The measured dispersion

2
REACTOR RADIATION DIVISION PROGRAMS

0.50

M

I

h- > 0.40

en

LU

ien 0.30

o

>-

jg 0.20

LjJ Q

~Z. o

o 0.10

Q_

ORNL-DWG 75-3586

1 !

PdD

PdH

i I IV I \.a. i7\ ,1 1 , , , , i , , , . I , r, ,4 , , , I , ,

,

4 8 12 16

FREQUENCY (THz)

20 24

Figure 1. Phonon density states in PdD and PdH, calculated from the

twelve parameter Born-von Karman fit to the neutron scattering

data for PdD_ ,_.

0. 63

relations are shown in figure 2, and the derived frequency distributions

are shown in figure 3.

Several interesting features of this system of alloys are apparent

from the results shown in these figures.

1. The marked positive dispersion in the transverse acoustic

modes which is characteristic of pure Nb decreases as deuterium is added.

2. The dip in the [100] longitudinal acoustic branch near C=0.7

persists even in the NbD , r results.

3. The "kink" in the [110] L branch near ^=0.35 is present in

3
REACTOR RADIATION DIVISION PROGRAMS

coon din

REDUCED WAVE VECTOR COORDINATE

CIIO]

Figure 2. The phonon dispersion curves of Nb

(

), NbD (full and

open circles) and NbD . (full and open triangles) at 473K.

Error bars are omitted for clarity.

Nb and NbD^ ir , but not in NbD„ , r 0. 15 0. 45

4. The shape of the [111] branches of NbD_ . r are quite different

0. 45

from those of Nb or NbD , especially near £=0.7, an area of particular

interest in connection with electronic instabilities.

5. The overall frequencies increase as deuterium is added, even

though the lattice parameter increases by over 2% in NbD , . This

behavior is opposite to that observed for PdD . x Many of the above features are undoubtedly connected to the complex

electronic structure of Nb and its alloys. This problem is extremely

complicated, but recent developments give some hope that our understanding

will improve soon. However, in the absence of such theoretical understanding, we can still make some progress by comparing the present

results to those of other authors for Nb-Mo alloys and to our own results

for PdD . From these comparisons, we can infer that the great majority

of the above features are due to rigid-band electronic effects because

of the similarity of the present results to the Nb-Mo alloy data.

4
REACTOR RADIATION DIVISION PROGRAMS

However, as expected, there are differences which must be ascribed to

local strain and non-rigid bond effects. It is hoped that the present

detailed results will lead to further theoretical progress in understanding these interstitial alloys.

FREQUENCY (THi) 3 4 5

10

ACOUSTC PHONON DENSITY OF STATES

NbD, AT 473K

-PURE Nb

-t-0.15 -1-0.43

15 20

ENERGY (m«V)

* 30

Figure 3 Phonon density of states for Nb

(

) NbD n .. c

( ) and NbD_ ._

* 0. 15 U. 4j (—) . The arrows denote critical points or other points of

high phonon density suggested from data of figure 2.

3. The Diffusion of Hydrogen in Polycrystalline Thorium - J. M. Rowe,

and J. J. Rush

Tn collaboration with Kurt Skold, C.A. Pelizzari and H. E. Flotow

at Argonne National Laboratory, we have obtained preliminary results on

the quasielastic scattering of neutrons from ThH and ThH

2Q

at

800°C. The data from these experiments are severely distorted by

scattering from the quartz sample containers, but preliminary analysis

suggests that the hydrogen in this fee metal occupies tetrahedral sites,

in contrast with the octahedral site occupation in fee Pd . This exciting
REACTOR RADIATION DIVISION PROGRAMS

result will be pursued in a single crystal sample of Th in a molybdenum

sample container in collaboration with J. G. Traylor of Ames Laboratory.

4. Lattice Dynamics of Vanadium Deuteride - J. J. Rush, J. M. Rowe

and N. Vagelatos

Some preliminary phonon measurements have been made in a study of

lattice dynamics of vanadium deuteride (VD ) single crystal using the

BT-9 three-axis spectrometer. Acoustic phonons up to 15 meV have been

observed, but great difficulty has been experienced at higher energies

due to very high incoherent background and the shape of the dispersion

curves. Experiments and analysis are continuing.

CRYSTAL DYNAMICS, PHASE TRANSITIONS AND ORIENTATIONAL DISORDER

IN IONIC CRYSTALS

More work has been completed in our continuing studies of the

dynamics of interatomic forces, rotational disorder and phase transitions

in prototype orientationally disordered crystals. The precise nature of

the orientational disorder and interatomic forces in the various crystal

phases of broad classes of analogous solid materials is not generally

well understood, nor is the microscopic basis of the changes in physical,

thermodynamic and mechanical properties associated with the related

order-disorder transitions.

Our research during the past year has concentrated on careful

studies of the lattice dynamics of ND. I and alkali cyanide single

crystals by coherent neutron scattering, although some optical (KCN) and

quasielastic scattering (ND I) measurements were also done on these

systems. Preliminary reports on previous measurements have been made in

last years' progress report (NBS Tech. Note 860).

1. Alkali Cyanides - J. M. Rowe, J. J. Rush, N. Vagelatos, N. J. Chesser

During the past year we have completed a study of the crystal

dynamics of KCN and NaCN in their disordered (NaCl) cubic phase by

6
REACTOR RADIATION DIVISION PROGRAMS

coherent inelastic scattering and infrared reflection techniques. We

have also obtained new information on the nature of the cubic-orthohombic

phase transition in these crystals and its relationship to the lattice

dynamics by a careful, high resolution measurements of the acoustic

phonons (including soft shear modes in the [100] and [110] directions in

these crystals as a function of temperature)

.

In general the observed acoustic phonon intensities were superimposed on a varying "background" (non-one phonon scattering) which

tended to increase as measurements were extended to higher energy phonons.

The phonon intensities were also unusually weak, particularly at higher

energies and q values. In fact we have thus far been unable to clearly

30

20

>a>E

T—i—i—i—i—r- NaCN

• T

OL

-NaBr

DBUnassigned

•Atr 30

20-

KCN

• T OL

-KBr

//-

0.5 cCCod cooCi]

REDUCED WAVE VECTOR COORDINATE

0*03

1

i cCCco

Figure 1. Acoustic phonon branches measured for NaCN and KCN at room

temperature. The TA and LA dispersion curves for NaBr and

KBr (solid lines) are also shown for comparison, as are the

long wavelength slopes (dashed lines) of the acoustic branch

determined from the measured elastic constate.
REACTOR RADIATION DIVISION PROGRAMS

assign any optical vibration frequencies from our neutron measurements.

Phonon frequencies measured and assigned for KCN and NaCN in the

[001] direction are shown in figure 1. It is difficult to give a clear

explanation of the large background and lack of observation of phonon

peaks at higher energies. It would seem that a combination of factors

such as multiphonon scattering and other scattering processes involving

the hindered rotations of the disordered cyanide ions , must provide the

large background observed in our phonon scans. We also suspect that

phonon lifetimes in these crystals are decreased significantly through

interaction of the translational modes with the large amplitude rotational motions of the cyanide ions. This likely provides at least part

of the reason that phonons do not appear to exist (according to our neutron measurements) as well characterized excitations in the cyanide

crystals at higher frequencies and finite wave vectors.

Comparison of the cyanide dispersion curves with comparable measurements for KBr and NaBr (figure 1) show some significant differences.

For example the LA[100] branch of NaCN shows no evidence of the dip in

frequency exhibited close to the zone boundary by the KBr and NaBr

dispersion curves. In fact, the shape of the measured branches for the

cyanides is similar to that predicted by a rigid ion force model, while

the alkali halides generally require a more completed "shell" model

which takes into account ionic polarizability . A more interesting

feature is the positive dispersion shown at low L, in the [001] TA branches

in both KCN and NaCN. This is associated with' what appears to be anomalously low mode frequencies close to the zone center, as indicated by the

fact that both NaCN and KCN are lower in frequency than the corresponding

bromides. This observation is consistent with recent elastic constant

(ultrasonic) data on KCN which show that C. . decreases rapidly as the

44

temperature approaches the phase transition (167. 5K)

In view of these results we have initiated a series of highresolution phonon measurements in both KCN and NaCN down to the cubicorthohombic phase transition. Some preliminary results of these
REACTOR RADIATION DIVISION PROGRAMS

measurements are shown in figure 2, where we have plotted the observed

phonon energies for the [100] TA branch for KCN at 293 and 175K.

These phonon results (and similar measurements for the [110] TA branches)

provide clear evidence that the phase transition is associated with a soft shear mode. The shape of the phonon peaks observed at £=0.1 are shown in figure 3, and again illustrate a clear soft mode behavior,

with the phonon peaks approaching zero frequency and very large relative

widths as the temperature is lowered. There are several notable features

of our preliminary results: (1) The onset of "soft" behavior occurs

over a wide temperature range and terminates in a first order phase

transition. (2) The dispersion curves are "soft" more than half way

across the zone. (3) The (in) ability to observe higher energy phonons

is not changed by lowering the temperature. A particularly interesting

and challenging question is the nature of the correlation of the orientational disorder of the cyanide ions with the observed soft mode behavior,

We are extending our measurements on this system to a careful study of

phonon line shapes and elastic scattering behavior, as well as to phonon

measurements at higher temperatures. Further neutron diffraction investigations of the cubic and orthohombic phases are also planned.

2. Ammonium Iodide (ND.I) - N. Vagelatos, J. M. Rowe and J. J. Rush

The analysis of the phonon-dispersion curve measurements for ND.I

in its NaCl phase described in our last report have been completed.

This work provides the first detailed information on the lattice dynamics

and crystal force fields in the high-temperature phase of an ammonium

halide. In addition, since the orientationally-disordered high temperature-phases of ND.I and the alkali cyanides are isomorphous, a com- parison of the ND.I and KCN (and NaCN) results should be useful in

assessing the effect of rotational disorder on the crystal dynamics and

character of the phonons in such crystals.
REACTOR RADIATION DIVISION PROGRAMS

8

t

6

-z. UJ

KCN DOOH TA

* «

l

t

$

.•• +

t • 296K

I75K

I I 0.2 0.4 0.6

hcu (meV)

0.8 1.0

Figure 2. Transverse acoustic phonon branches of KCN in the [001]

direction at 296 and 175 K.

The measured dispersion curves for ND.I are shown in figure A,

along with the (16-parameter) fits obtained by analyzing the data in

terms of "simple" and "breathing" shell models with general repulsive

short-range forces out to second neighbors. In these models both ions are considered to be spherical and polarizable. The "breathing" shell

model, which takes into account the isotropic deformation of the spherical

shells, gives the best overall fit to the data. In addition the model

predictions for the bulk crystal properties (shown in table 1) are generally in good agreement with observations, with the "breathing" model

again providing better overall agreement. The character of our results

closely resemble those of the alkali halides. It should also be noted

that a separate time-of-f light neutron spectrum measurement suggests the

absence of well-characterized torsional mode phonons, so that no attempt

was made to investigate the rotational modes by the triple-axis method.

10
REACTOR RADIATION DIVISION PROGRAMS

O

o

o

en

\-3

LxJ

KCN

£=0.! at (-0.1,2,0)

TAH^OOH

AE =O.I7meV

-0.2 -0.4 -0.6 -0.8 -1.0

T)cij(meV)

Figure 3. Smoothed representation of the measured [00^] TA temperature

(Transition temperature = 167.5 K)

11
REACTOR RADIATION DIVISION PROGRAMS

-i 1 1 1 1 1 1 1 r -i 1 1 r

10-

— 16 Parameter BSM @ T2 — 16 Parameter SSM O L a T,

T O L

0.5 EI003

0.5 CIIIJ

1.0 0.5 EMOJ

REDUCED WAVE VECTOR COORDINATE

Figure 4. Measured phonon dispersion curves for ND, I at 296 K) and the

4 16-parameter simple and "breathing" shell model fits.

The breathing shell model fit was used to derive the transiat ional

phonon frequency distribution, g(v), for ND. I, which is shown in figure

5. The structure of the calculated g(v) displays critical-point and

cut-off frequencies in close agreement with the details of the measured

dispersion curves in figure 4, moreover the mean-square vibrational

amplitudes are in excellent agreement with those derived from earlier

neutron diffraction work and thus would seem to rule out the conclusion

(from the diffraction results) that the rather large thermal amplitude

> °2

(^0.05A ) indicate static displacements away from their face-centered

positions.

12
REACTOR RADIATION DIVISION PROGRAMS

<

>- h- 2 m

UJr>

CO

u.o o > UJ H or

LL —, CO

*: 2

CJ> Q

CM __

(- <r O Q X

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>>

4-) « o •H co si CO C

^J c o

CJJ •H

ac T) — ^H 1—

1

co CO a 4-1 CD O X » 4J 4-J

j—

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<r ,—u Q o 2 U-l

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j

CO 4J CO

CD > 4-1 U O

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£ CO >^ CO C

4-1 5-j tu •—

i

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.

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13
REACTOR RADIATION DIVISION PROGRAMS

Finally it is interesting to compare these lattice dynamics results

with those described above for the analogous (fee) phases of the alkali

cyanides. The fact that phonon dispersion curves (including the optic

modes) were successfully measured for ND. I strongly suggests that

the high molecular reorientational rates do not greatly affect translational phonon lifetimes. The fact that the rotational disorder in the

cyanides apparently does seriously perturb the existence or lifetimes

of higher energy phonons suggests several possible explanations: (1) the

Table 1. Bulk properties of NB I calculated from SSM and BSM model

parameters compared to observed values for NH. I.

Property SSM(ND.I)

4

C

11

(10

11 d/cm2

) rL " 12

C

" L 44

-12 2 (10 cm /d)

2.82±0.08

0.85+0.08

0.32±0.02

4.4211.27

6.62±0.27

BSM(ND.I)

4

2.55±0.03

0.74+0.03

0.26±0.01

9.78±11.60

1.94±0.24

7.41+0.13

OBSERVED (NH. I)

4

2.448

0.428

0.240

9.8

2.90

^6. 6

hindered rotational modes in the alkali cyanides interact with

the translational motions of neighboring ions, since the rotational

modes are expected to have energies (^10 meV) in the range of the

translational modes, (2) the reorientations of the linear CN ions

affect the lifetimes of the translational vibrations more strongly than

the tetrahedral (pseudospherical) ND, ions.

We intend to pursue our measurements on ND.I further to (1) a quasielastic scattering study of the ND, reorientation behavior and

(2) further lattice dynamics studies close to the fcc+->bcc transition.

14
REACTOR RADIATION DIVISION PROGRAMS

SYMMETRY ANALYSES OF NEUTRON SCATTERING IN CRYSTALS - APPLICATION

OF TIME REVERSAL SYMMETRY

R. C. Casella, J. M. Rowe, and S. F. Trevino

Work has continued on the algorithm stated earlier by Casella for

computing the number of independent real parameters in the phonon dynamical matrix. Firstly, a clearer conceptual distinction has been drawn

between the number of real parameters in the phonon dynamical matrix at

fixed wave vector k and the number of real parameters in some assumed

model potential (designed to reproduce the spectrum at all k ). Secondly,

the algorithm has been applied to several illustrative cases: Zinc

-> -* Blende with k along A and A in the Brillouin zone, diamond with k

along A, graphite with k at A, and wurtzite with k along R. The results were compared with the computer generated dynamical matrices of Warren

2 and Worlton where conceptional difficulties of several types are found,

particularly the need to count independent real parameters rather than

matrix elements. All ambiguities in the Warren-Worlton procedure are cleared up via application of the algorithm in ref. 1. A summary of our results may be found in table 1. Of particular interest is the case of

wurtzite for k along the line R. Whereas the procedure in ref. 2 leads

to 77 to 80 real parameters, we see from table 1 that the properly

reduced dynamical matrix can contain no more than 34 real parameters.

This case (II-c, in the nomenclature of ref. 1) refers to one where a representation sticks to itself due to time reversal symmetry.

1. R. C. Casella, Phye. Eev. Bll, 4795 (1975).

2. J. L. Warren and T. G. Worlton, Argonne National Laboratory Report

ANL-8053 (1973). [Available from Natl. Tech. Info. Service,

U.S. Dept. of Commerce, Springfield, VA]

15
REACTOR RADIATION DIVISION PROGRAMS

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16
REACTOR RADIATION DIVISION PROGRAMS

THEORETICAL ANALYSIS OF PHONON DECAY WIDTHS IN KCN, N aC N

R. C. Casella

Previously, an analysis of the Debye-Waller factor for heteronuclear

diatomic "free rotators" in a vibrating lattice has been carried out.

These affect the amplitude of phonon and rotator induced peaks in inelastic neutron scattering via an effective renormalization of the Fermi

nuclear scattering amplitudes. However, the decay widths require separate analysis. Since, recently, N. Chesser has obtained data on the

frequency and temperature dependence of these widths in KCN, including

particularly, those of the soft TA mode, I have begun a theoretical

analysis of the line-width problem for these systems, aided by insights

provided by the experimentalists, N. Chesser, J. Rush, and J. M. Rowe,

associated with various aspects of the problem. An attempt is underway

to separate the effects of mode softening from those of strong interaction with (localized) hindered-rotator modes, the existence of which

is evidenced in independent experiments.

THE USE OF POSITION SENSITIVE DETECTORS IN SINGLE CRYSTAL

DIFFRACTOMETERS

E. Prince and A. Santoro

In recent years quantum counters have been developed for x-rays and

neutrons which produce output pulses whose amplitude is a function of the

linear position along the center wire at which the quantum was absorbed.

Such position-sensitive detectors (PSDs) make possible a large increase

in the efficiency of data collection in single crystal dif f ractometers

,

particularly for crystals with complex structures and correspondingly

large unit cells. In view of the interest of the Reactor Division in

the analysis of crystal structures involving large molecules, we have

carried out a study of the possible designs of single crystal diffract17
REACTOR RADIATION DIVISION PROGRAMS

Figure I Schematic representation of the flat-cone geometry. The

crystal in figure is rotated about the c-axis and the angle

u is adjusted so that the Jt-th level of the reciprocal lattice

is in flat-cone position (the plane of the level is perpendicular to the plane of figure) . The circle is the trace of the

intersection of the reflection sphere with the plane of figure.

(*) ometers utilizing linear PSDs , and of the related problems of data

collection and processing.

In order to utilize the properties of the linear PSD it is necessary

to arrange for many diffracted beams to pass through the sensitive volume

of the detector. While there are a number of possible ways to achieve

that objective, for example the detector could be made to simulate the

motion of a row line in a precession camera, the most straightforward

Although two dimensional PSDs have been constructed, they are still in an early stage of development, and have not been considered in our

study.

18
REACTOR RADIATION DIVISION PROGRAMS

system Is to arrange for all of the diffracted beams corresponding to

points in a layer of the reciprocal lattice to be on a common plane.

This is accomplished by using the flat-cone Weissenberg geometry. The

crystal is mounted so that it may be rotated around a zone axis normal

to a set of dense planes of the reciprocal lattice, and oriented with

respect to the primary beam so that the lattice points of any desired

layer will intersect the reflection sphere on a great circle. If the

detector lies in the plane of the great circle it will intercept all

diffracted beams from that layer (figure 1)

.

C-AXIS

e-th LEVEL

ZERO LEVEL

i//- ROTATION

DETECTOR?

PRIMARY

BEAM

Figure 2. Sketch of a four circle diff Tactometer adapted to the flat cone Weissenberg geometry. The conventional (J> , x an<3 to circles of the dif fractometer permit to rotate the crystal

about more than one zone axis with a single setting of the

crystal.

19
REACTOR RADIATION DIVISION PROGRAMS

A disadvantage of the flat-cone geometry is that, for upper levels,

there is a region of reciprocal space which is not accessible to the

dif f ractometer . If the rotation around the zone axis is performed by a single circle, a remounting of the crystal will be necessary to measure

reflections in this region. However, if we perform the rotation of the

crystal by using the three independent angles of a four circle diffractometer more than one zone axis may be used with a single setting of the

crystal. Figure 2 shows how a PSD may be mounted on a four circle diff ractometer to take advantage of the flat-cone geometry.

If, due to crystal symmetry, the chosen zone axis is also a reciprocal lattice row, the flat-cone method, like the equi- inclination and

normal-beam methods, has the undesirable property of intrinsic simultaneous diffraction. For complex organic crystals such as proteins this

is unlikely to be a problem, but for certain inorganic crystals great

care will be needed to avoid systematic errors in intensity measurements.

The use of PSDs is associated with two important features in the

intensity measurement procedure which are not present in conventional

counter methods. First, the peak and background intensities of several

reflections may be measured simultaneously, and, second, the counter's

horizontal width needed for the measurements of integrated intensities is

not fixed by slits, but can be determined by computer for each reflectlon ( *>.

In a typical data collection procedure (the dif fractometer is

assumed to be under real time control by a computer) the crystal is

rotated in small steps around the rotation axis. In each step position

quanta are counted for a specified length of time, and accumulated

counts are stored in a buffer according to the position in the detector

at which they were detected. At the end of the counting interval the

buffer is examined and for all detected counts a determination is made

whether they come from a region near a reciprocal lattice point or from a background region. Counts corresponding to a peak or to a

*The vertical width is fixed by the lateral extent of the sensitive

volume of the linear detector and cannot be adjusted.

20
REACTOR RADIATION DIVISION PROGRAMS

background are stored, while the others need not be retained. The same procedure is repeated for each step position. A complete reciprocal

lattice layer is examined by a complete revolution around the rotation

axis.

The dif fractometer settings and the conditions required for the

measurement of integrated intensities have been evaluated by adapting

known procedures to our particulary geometry (Burger, 1942; Busing & Levy.

1967; Burbank, 1964; Alexander & Smith, 1962; 1964a; 1964b).

1. L. E. Alexander and G. S. Smith, Acta Cryst. 15, 983 (1962).

2. L. E. Alexander and G. S. Smith, Acta Cryst. 17_, 447 (1964a).

3. L. E. Alexander and G. S. Smith, Acta Cryst. 17, 1195 (1064b)

4. M. J. Buerger, X-ray Crystallography (1942) Wiley, New York.

5. R. D. Burbank, Acta Cryst. 17, 434 (1964).

6- W. R. Busing and H. A. Levy, Acta Cryst. 72_ y 457 (1967).

THERMAL NEUTRON FLUX MEASUREMENTS

V. W. Myers and M. Ganoczy

Analysis of the data for the measurement of the absolute thermal

neutron intensity of a beam by means of a manganese sulfate bath is

continuing. The beam was used for activating boron loaded cobalt glass

beads which are essentially black to thermal neutrons. A thermal flux

can then be determined by activating a bead in the unknown flux and

comparing the counting rate to that of a bead activated in the known

thermal beam.

Activation and decay times for Co-60 enter, of course, into the Cocomparison. The long half-life Co-60 (^5 years) is advantageous in

that an activated bead can be used for several years.

21
REACTOR RADIATION DIVISION PROGRAMS

NEUTRON RADIOGRAPHY

H. Berger, M. Ganoczy, and V. Myers

and

W. Parker

(Reed College, Portland, OR)

A survey of the neutron radiography community was conducted

to determine the needs for standards in this expanding method of

nondestructive evaluation. Representatives of more than 50

organizations including universities, government laboratories, and

commercial suppliers were contacted in the survey. The results

show that there is strong interest in, and support for the

development of standards for neutron radiography and gauging.

The standards needs as determined by this survey are given

below in priority order:

1. Define divergence characteristics of neutron radiographic

beams in order to determine sharpness qualities of

radiographs of thick objects.

2. Characterize neutron beams used for through-transmission

and scatter gauging so that test data can be more thoroughly

understood and interpreted.

3. Better define neutron spectral measurements over present

ASTM image quality indicator (IQI) capability, and also better

define gamma content of beams (including an improved measure

of gamma energy) in order to better interpret test results.

4. Develop beam characterization methods better suited to low

neutron intensity, relatively high gamma content non-reactor

neutron sources (such as radioactive and accelerator sources)

.

5. Develop image quality indicator (IQI) methods for nonfilm

detectors such as real-time, track-etch, gas-cell, etc., to

take into account differences in viewing methods, neutron

spectral and gamma sensitivity, and motion response.

22
REACTOR RADIATION DIVISION PROGRAMS

6. Develop concepts for standards for neutron inspection methods

employing neutrons in the cold, resonance, epithermal, and

fast energy ranges.

The MBS program in neutron radiography is being adjusted to

reflect the needs and interests shown by this survey. A report on

the study was issued and sent to survey participants in May and

June, 1975. Additional information obtained from comments on the report

will be factored into the program plans.

Inputs for an ASTM Recommended Practice For Thermal Neutron

Radiography have been collected and are now being placed in a single document to be submitted to ASTM Committee 37.05, Neutron

Radiography. The document will discuss procedures for good quality

thermal neutron radiography.

An additional collaborative effort with ASTM resulted in an NBS-ASTM Symposium on Practical Applications of Neutron Radiography

and Gauging, held at NBS Feb. 10-11, 1975. The 150 attendees heard

28 papers during the two-day meeting. Papers were presented on subjects ranging from biological applications to those involving

explosives, ordnance, adhesives, rubber, electronic components, wood,

nuclear fuel and museum objects. The proceedings of the meeting

will be published by ASTM as Special Technical Publication 586.

A new neutron radiography beam facility at the reactor has been

designed and construction of components has begun. The new beam will

provide higher neutron intensity (thereby permitting improved

collimation potential) , and a broad neutron spectrum. The anticipated

neutron intensity for the new vertical beam facility will be greater

8 2 than 10 n/cm s at medium collimation and will provide approximately the

f< 7 same intensity as the thermal column beam (2 x 10 n/cm s) but with a collimator L/D ratio more than ten times greater (1000 vs. 90). This

collimation will permit the production of high resolution thermal

neutron radiographs.

The spectrum broadening of the new beam will also provide a major advantage. Beam filtering can be used to provide either a beam

23
REACTOR RADIATION DIVISION PROGRAMS

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25
REACTOR RADIATION DIVISION PROGRAMS

that is primarily cold or a beam of epicadmium neutrons (anticipated

cadmium ratio with gold is less than 5 versus 600 for the present

thermal column beam) . The high intensity will offer an advantage

because even after filtering, exposure times will not be unduly long.

An experiment was performed to obtain these design data.

Another possible use of the greatly increased intensity of the

beam from the new facility is the use of a large metallic single

crystal to form a crude neutron dif fractometer , thereby making possible

neutron radiography with approximately monoenergetic neutrons and with

reasonable exposure times.

An unusual feature of the new beam will be the capability to

change collimation ratio (input aperature size) and also to filter

the beam remotely while the reactor is in operation. This will be

accomplished by rotating assemblies containing apertures or filter

materials. A diagram of the vertical beam design is shown in figure 1.

Application studies during the past year have involved a variety

of samples. Work reported last year on the characterization of fatigue

cracks has continued, in collaboration with D. G. Eitzen, NBS Mechanics

Division. Progress includes a more uniform contrast material to fill

the crack (gadolinium nitrate dissolved in either oil or water) and

better control over the angular orientation of the crack. This is

illustrated in the series of neutron radiographs shown in figure 2.

Further work is planned with Gd-157 enriched contrast agent material

to see what angulation can be used to visualize the crack front.

Application studies to show the potential of thermal neutron

radiography have continued with several government and industrial

organizations. An interesting application study has involved samples

of carbon cloth impregnated with phenolic resin, a material of interest

for rocket applications. The neutron radiographs of a series of samples

containing different amounts of resin demonstrated that thermal neutron

radiography was capable of differentiating voids from resin concentration

differences

.

26
REACTOR RADIATION DIVISION PROGRAMS

New developments in thermal neutron image detection include the use of a new single-emulsion film and progress in real-time neutron

radiography. Electronic integration systems have been used with the

real-time system to show that useful low-intensity, thermal neutron

images can be obtained by television integration methods. Tests

3

9 were made at intensities as low as 10 n/cnT.s, an intensity sufficiently

low that normal 1/30 second frame time images were barely detectable;

useful images could be brought out by image integration times in the

order of minutes

.

Neutron image tests have also been made with a film originally

made for electron imaging (Eastman Kodak Type FE 4721) . Tests are still in progress but it has been shown that the speed for neutron

imaging with gadolinium metal screens is about equal to Type M X-Ray

Film. The new electron-sensitive film offers the advantages of a single emulsion - namely improved spatial resolution and relative

neutron-gamma response.

Some preliminary studies have been made to investigate methods

for three-dimensional thermal neutron radiography. The method involves

the superposition of radiographs taken from different angular

1 2 orientations. ' This permits one to focus a given image plane while

other, undesired image planes are blurred. By moving the films with

respect to one another, the observer can choose the desired image plane.

3 In previous three-dimensional x-ray and gamma radiography, the

radiation source was moved linearly to obtain the different angular

radiographic views. In these thermal neutron tests, the objectdetector combination is rotated to obtain the different angular views.

It has been shown that these two motions yield identical results if

the object-detector rotation motion is combined with some linear axial

movement between source and object-detector. The axial movement (along

the line connecting the source and object-detector) compensates for

changes in geometric magnification. The neutron work has also clarified

the necessity to hold source-object distances reasonably small in order

to effectively separate images from different object planes. Further work

27
REACTOR RADIATION DIVISION PROGRAMS

is planned to determine spatial resolution capabilities at different

depths in the radiographic object.

1. E. R. Miller, E. M. McCurry and B. Hruska, Radiology, 9_8,

249-255 (1971).

2. A. G. Richards in Biomedical Sciences Instrumentation, Instrument

Society of America, Pittsburgh, Pa., Vol. 6, pp. 194-199 (1969).

3. N.. P. Lapinski and H. Berger, Trans. Am. Nuclear Soc, 17_,

pp. 178-179 (1973).

Work done in collaboration with N. P. Lapinski and K. J. Reimann,

Argonne National Laboratory.

GAUGE THEORIES

R. C. Casella

As noted in the previous report, the Salam-Weinberg utilization of

Yang-Mills gauge fields to unify the weak and electromagnetic interactions

has successfully predicted the existence of weak neutral currents. Central

to such theories is the question of "mass generation" via Higgs scalars

(or otherwise, e.g., dynamically) and its relation to gauge symmetry and

its breaking (analogue of Landau's theory of second order phase transitions in chemical physics) . In quantum electrodynamics (QED) it is

usually held that the masslessness of the photon is a direct consequence

of the gauge invariance of electromagnetism. Since this question is

of importance to the more general theories as well, we have re-examined

it in the context of the canonical Dyson-Salam-Ward renormalization

program (perturbation theory) . While it is obvious that the inclusion of mass terms in the unperturbed Lagrangian destroys gauge invariance, the

usual argument' for the absence of mass generation via interaction is

found wanting. Granted that the Ward-Takahashi identities, which follow

28
REACTOR RADIATION DIVISION PROGRAMS

2 from current conservation, lead to the transversality condition

k n (k)=0 for the vacuum polarization tensor n PV

(at four-momentum k)

,

it is nevertheless our view that one can conclude therefrom only

uv , . . yv y v „ 2 Ntt/1 2* n (k)=(g -k k /k )n(k ), (1)

rather than the usual assumption ,

yv, . , yv. 2 ^.v.^ ,,2, n (k)=(g H k -kM k )n (k ). (2)

(g is the metric tensor.) Eq. (1) follows naturally as a solution to

the Dyson equation for the radiatively corrected photon propagator

Hi'v^ since (!) has the same form as the unperturbed propagator D (k)

9 yv when D^ is written in the Landau form. Since H(k ) is presumably

analytic in k about the (unperturbed) mass-shell point, k

2 =o, we may

write

n(k

2 )=n(0) + k

2 n (k2

), (3)

2 2 where IT (k ) is also analytic in k . Moreover, the Dyson equation

reduces to

D' _1

(k

2 )-D

_1

(k

2 )-n(k2

), (A)

-12 2 2 where D (k )=k , whence it follows from (3) that provided n(0)=0, D' (k ) 2 has a pole at k =0; i.e., the mass of the photon remains zero under the

effects of interaction. That is, if IT(Q)=0, Eq.(l) and Eq. (2) are the same

and the usual argument holds. However, when 11(0)^0 Eq.(4) yields a pole

2 2 2 in D' (k ) at k =m M1(0); i.e., a dynamically generated photon mass

3 4 1

appears. ' The usual assumption that the W-T identities imply (2) rather

than (1) cannot help but lead to zero photon mass since, from the point

of view of (1), 11(0) has been arbitrarily set equal to zero in writing

(2) . In QED, where the photon mass is known experimentally to be compatible with zero (stringent limits exist), the distinction drawn here is a fine one, but this need not be the case for the more general gauge

29
REACTOR RADIATION DIVISION PROGRAMS

theories. Mechanisms for mass generation without Higgs scalars are currently being investigated.

1. See, e.g., J. Bjorken and S. Drell, Relativistic Quantum Fields

(McGraw-Hill, New York, 1965) or S. Schweber, Introd. to Relativistic

Quantum Field Theory (Row-Peterson, Evanston, II, 1961).

2. Current conservation and gauge invariance are intimately related.

3. Albeit infinite or cut-off dependent and removable via renormalization.

2 4. The expression for m is approximate in the perturbative sense

(assuming a cut-off). Precisely m^ is a solution of the equation, m

2 -n(0)-m2 n

i

(m

2 )=0

30
B. RRD-NBS Collaborative Programs

TOTAL PROFILE ANALYSIS IN NEUTRON POWDER DIFFRACTOMRTRY

A. Santoro and E. Prince

and

A. D. Mighell

(Inorganic Materials Division)

and

C. S. Choi

(Picatinny Arsenal, Dover, NJ)

The powder method has been employed in crystal structure

analysis in all those cases in which suitable single crystals

cannot be grown. The method has gained in importance especially

in neutron diffraction, due to the difficulty of obtaining specimens

of sufficiently large dimensions for single crystal work. The usual

technique of integrating under the Bragg peaks to obtain the intensities

of each reflection can only be applied to well resolved diffraction

lines, i.e. to very simple structures. For structures of moderate

complexity and low symmetry there is considerable overlap of the

independent peaks in the power diagram and the application of

conventional methods of analysis results in a serious loss of information,

In these cases it is of particular importance to develop techniques

for extracting from the complex profile of a powder pattern the

maximum amount of information. The method recently proposed by

Rictveld does not attempt to measure the intensities of individual

Bragg reflections, nor those of separate groups of overlapping

peaks, as it has been done so far. The method, instead, makes use

of the total profile of the powder pattern, including the regions

where there is no measurable diffracted intensity, to decide if any

given structural model is consistent with the observed data and to

refine the parameters of the model by least squares analysis. These

computations can be carried out only if the theoretical shape of the

31
RRD-NBS COLLABORATIVE PROGRAMS

diffraction lines is known. Peak shapes of single diffraction lines

are Gaussian for most neutron dif fractometers , while in the case of

x-rays a satisfactory function for describing single peaks has not

RbSH — CALCULATED

• 06SCKVE0

64 4764 4B64 4964 5064 56 59

Figure 1. Observed and calculated neutron powder pattern for structure

of the room temperature phase of RbSH. The final refined

parameters for the structure are:

a = b = c = 4.526(12) A

9 = 3 = y = 69.39(1)

Atomic coordinates

Rb-- Hi2 2 2

Space group R3m

S:

rfl : X X X

-rH: xxx, x = 0.1252

Isotropic temperature factors

B

Rb

= 3 ' 21

B_

D =1.25 B

B^ = 8.39

Rb

n

32
RRD-NBS COLLABORATIVE PROGRAMS

yet been found. The Rietveld procedure, therefore, can be applied

only to neutron powder patterns.

Total profile analysis, if properly used, can be competitive

with conventional single crystal procedures, at least for structures

of moderate complexity. This means that it is often possible to

refine a structure equally well with a powder pattern recorded in one day or with a set of single crystal intensity data collected

over a period of days or weeks. In view of this important

advantage, combined with the ease with which samples can be mounted

and handled on the powder method, we have applied the Rietveld method

to a number of problems now under investigation in the Reactor

Division. The results of the refinement of the room temperature

structure of RbSH are shown in figure 1 as an example. Efforts are now under way in this division to devise crystallographic methods

for the generation of structural models in phase transformation

studies. The completion of these investigations will considerably

expand the measurement capabilities of the neutron spectrometers

now in operation at the NBSR.

CONFORMATION OF POLYMERS IN DILUTE SOLUTION

C. Han

(Polymer Division)

and

B. Mozer

Conformation of polymers in dilute solutions are being studied in

small angle scattering experiments. Both deuterated polystyrene-poly

(methyl methacrylate) , (dPS-PMMA) diblock copolymer, and deuterated

polystyrene (dPS) homopolymer which is the precursor in the anionic

polymerization have been chosen for this study. Deuterated toluene is

used as the solvent in both cases. The coherent scattering cross- sections of deuterated styrene to that of methyl methacrylate has a

33
RRD-NBS COLLABORATIVE PROGRAMS

ratio about 1 to 100. Therefore, the PMMA block should have a very

strong contribution to the scattering function S(k) in the diblock

copolymer case. In the preliminary study, we have been able to obtain the radius

2 1/2 ° of gyration of the 90,000 molecular weight dPS, <S > ' =120A. The

scattering function indicates that dPS exhibits a Gaussian chain distribution in toulene with an expansion coefficient v^l . 1 which was

obtained- in the asymptotic limit of large k

lim S(k) = Ax where x=k <S >

x-x»

Some results for dPS-PMMA have been obtained. A pronounced difference

in the scattering function was observed compared to that of the homopolymer,

This difference may be caused by the interaction of polystyrene and

poly (methyl metacrylate) segments which do not exist in the homopolymer

case. More experiments on this system are still underway.

The scattering function of deuterated toluene which is the solvent

as well as the major background source in the scattering experiments

°-l

above, have been measured up to k^9.0A

with x-ray results and theoretical models,

°-l

above, have been measured up to k^9.0A . This scattering will be compared

HYDROGEN BONDED DINERS IN SnHP04

L. W. Schroeder

(Polymers Division)

and

E. Prince

Since the last progress report we have learned that Professor

K. Ericks of Boston University has collected new x-ray data and further

refined the crystal structure of SnHPO. . The new refinement confirms

-2 the previous length of 2.52A for the hydrogen bonds linking the HP0,

34
RRD-NBS COLLABORATIVE PROGRAMS

o ions into dimers. The length of 2.52A together with some features in

the infrared and Raman spectra of this materials suggest proton tunneling.

As soon as we obtain more accurate atomic coordinates from Professor Ericks

we will proceed with the structure refinements using the neutron data.

35
C. Interagency and University Collaborative Programs

CRYSTAL STRUCTURE OF I,

3

> 5-TRrACETO-2 5 A,6-HEXAHYDftO-S-TRIAZI7INE (TRAT

C . S . Choi and P . Mannkas

(Picatinny Arsenal, Dover, NJ)

and

A. Santoro

The compound 1 ,3 ,5-triaceto-2 ,4 ,6-hexahydro-s-triazine , hereafter

referred to as TRAT, is one of the byproducts in the reaction of

hexamethylenetetramine with acetic anhydride. Chemically, TFAT is

related to cyclotrimethylene-trinitramine, commonly called RDX and a well known explosive,

COCH3

HXOC-N

n

N-GOCH, O-N-N N-N02

i n

Single crystals of TRAT were obtained by slow cooling of a chloroform

solution. Crystal symmetry and approximate all parameters were obtained

from precession photographs. The cell parameters were then refined by

least squares analysis from 16 reflections whose 28 angles were

determined with a dif fractometer . A summary of the crystal data is

given in table 1.

A total of 2484 independent reflections were measured with a

o 3-circle x-ray dif fractometer (A = 0.7107 A). The structure was

solved by direct and Fourier methods using programs of the X-PAY SYSTEM.

36
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

Table 1. Crystal data for 1, 3,5-triaceto-2 ,4 ,6-trlhydro-s-triazine

(TRAT)

Space group

a =

b =

c =

D = m

P2

1

/c

7.772(2) A

15.521(4) A

o 10.101(2) A

116.34

F(000) =

1.30 g cm

1.31 g cm

456

-3

Figure 1. Perspective view of the molecule of TRAT with thermal

ellipsoids

.

Full matrix least squares refinements with anisotropic temperature

factors for the heavy atoms and isotropic temperature factors for the

hydrogen atoms resulted in R values of R = 0.051 and R = 0.035. w

Figures 1, 2, 3 show, respectively, a perspective view of the molecule

with thermal ellipsoids, the unique bond distances and angles and the

packing of the molecules in the crystals.

37
INTERAGENCY AND UNIVERSITY COIIABORATIVE PROGRAMS

0(2) C(9)

C(8) 0(3)

Figure 2. Schematic illustration of the TRAT molecule with the

unique bond distances and angles. The standard deviations

on distances and angles are 0.004 A and 0.4°, respectively,

O ^&<o r^~ 3.378

Figure 3. Packing of the molecules in the crystal structure of TRAT.

The figure represents an orthogonal projection on the plane

perpendicular to a. 38
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

The general features of RDX and TRAT are very similar. However,

the molecular shape of the RDX molecule is much more distorted than

that of TRAT (in RDX the planes of the three nitro groups are inclined

to the plane through the carbon ring atoms of angles ranging from 18°

to 62°, while in TRAT the planes of the acetamide groups are inclined

to the plane of the carbon atoms with an average dihedral angle of

48°±2°).

Each ring carbon atom has short intramolecular contacts with

the oxygen and carbon atoms of the adjacent acetyl groups

o o (C...0 = 2.73 A and C...C = 2.93 A). The shortest intermolecular

o distances are 3.21 and 3.38 A for C...0 contacts. There is no evidence of hydrogen bonding in the structure.

THE CRYSTAL STRUCTURE OF MONOVALENT METAL AZIDES

C. S. Choi

(Picatinny Arsenal, Dover, NJ)

and

E. Prince

The crystal structure of KN (77K) , RbN (293K) and RbN (77K) were investigated as a part of the continuing study on the structures

o of monovalent metal azides. Using 1.226 A wavelength neutrons,

the reflections in one half of a hemisphere of reciprocal space were measured out to a maximum 20 of 105° for each crystal.

KN^ (77K)

A crystal with cylindrical shape, 4 mm in diameter and 5 mm

long, was used for this study. The unit cell dimensions were

o o a = 6.085(5) A and c = 6.997(5) A in the space group 14 /mem. The

structure was refined by the rigid body method, to the final R- indices

of wR = 0.040 and R = 0.029 for 80 observed reflections.

39
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

Table 1. N-N bond lengths before and after correction for the azide

libration. The shortest inter-ionic distances are based on parameters, corrected for the libration. The numbers given

in parenthesis are the N-N bonds corrected for the librations

obtained by Raman scattering.

Crystal N-N bond length

o (A)

o Cat ion-Anion (A)

Raw Corrected

6-NaN

3

1.162(1) 1.180 (1.177) 2.504

KN

3

(293) 1.174(1) 1.184 (1.183) 2.961

KN

3

(77) 1.183(1) 1.187 (1.187) 2.936

RbN

3

(293) 1.173(1) 1.187 (1.185) 3.099

RbN

3

(77) 1.182(1) 1.187 (1.186) 3.068

T1N

3

(293) 1.159(4) 1.181 3.037

T1N_(260) 1.164(1) 1.184 3.033

BMa 3^ 293K and 77K:

A small flat crystal, 0.5 x 2 x 4 mm, was used for this study.

RbN„ also crystallizes in the tetragonal space group 14 /mem, with unit

-J o o o cell dimensions a = 6.304(5) A, c = 7.53(1) A at 293K and a = 6.261(5) A,

o c = 7.44(1) A at 77K. The structures were refined by the method of

constrained rigid body refinement. The final R- indices were wR = 0.045,

R = 0.020 for 97 observed reflections of the room temperature structure,

and wR = 0.058, R = 0.045 for the 92 observed reflections of the

77K structure.

Summary on monovalent metal azides:

The N anions in the monovalent metal azide crystals are all

centrosymmetric and linear, and are bonded internally by a strong

resonance bond with double bond character. The thermal vibrations of

such azide atoms may be described quite accurately by the rigid body

40
INTERAGENCY AND UNIVERSITY COLIABORATIVE PROGRAMS

model since the amplitudes of the internal stretching modes in the

azide group are negligible compared to those of the rigid body motion.

The azide anions were refined with the constrained rigid body

Table 2. The librations of the azide anions obtained by the neutron

diffraction method compared with those obtained by Raman

scattering. Cruickshank's formula was used for the conversion:

6 2 =(h/8u2 Iv) coth (hv/kT)

Crystal Neutron Diffraction Raman Scattering

o L( ) v(cm ) v(cm ) L(°) v'(cm ) v(cm ) NaN 7.01 (110) (110) (6.42) 120 120

KN

3

(293) 6.00 (128 (5.28) 147

4.56 (172) (150) (5.14) 151 149

KN

3

(77) 3.51 (135) (3.17) 157

2.75 (197) (166) (3.07) 165 161

T1N

3

(293) 9.48 (81) (15.86) 48

5.64 (137) (109) (4.55) 172 110

TIN (260) 9.42 (77) (14.65) 49

4.75 (155) (116) (4.24) 175 112

RbN (293) 7.34 (105) (6.03) 128

5.03 (155) (130) (5.53) 140 134

RbN

3 (77) 3.84 (119) (3.44) 139

3.21 (154) (137) (3.16) 158 149

refinement method to give skewness to the end nitrogens without

increasing the number of variables in the refinement.

The interatomic distances in each crystal are summarized

in table 1. The observed N-N distances are quite different from

crystal to crystal and in the same crystal at different temperatures,

However, when the bond lengths are corrected for the effect of the

o libration, they all converge to a narrow range of values; 1.186 A,

41
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

within two times the observed standard deviations except for the

B-NaN„, as shown in table 1.

The librations derived from this diffraction study were compared

with the corresponding librations measured by Raman scattering, as given in table 2. The agreements between the two libration amplitudes

are quite satisfactory for all crystals except for T1N„. The amplitude

of libration in the TIN- crystals are too large to be harmonic, even

at 260K. The observed N-N bond lengths were corrected also for the

libration derived from Raman frequencies, as shown in table 1. The

two corrected bond lengths are essentially the same with maximum

o difference of 0.003 A. This suggests that the azide groups are essentially undergoing harmonic librations in these ionic crystals.

QUASI ELASTIC NEUTRON SCATTERING STUDY OF AMMONIUM- 1 ON

REORIENTATIONS IN AMMONIUM PERCHLORATE

H. J. Prask and S. F. Trevino

(Picatinny Arsenal, Dover, N. J.)

and

J. J. Rush

The rotational motions of ammonium ions in polycrystalline

NH.C10, have been investigated in the 55-150K temperature range

4 4

by means of quasielastic neutron scattering for a momentum transfer

°-l

range of 1-4 A . The gross behavior of the full-width at halfmaximum (FWHM) of the quasielastic peaks (figure 1) are consistent

with jump reorientations of either 180° about C^ axes or 120° jumps

about C_ axes of the NH, ion. The data are not consistent with

5 4

quasi-free rotation, rotational diffusion or 90° jump reorientations

about C„ axes of the NH. ion in the temperature range

2 4 examined.

Under the assumption that 120° jump reorientations about C

3 axes (breaking three hydrogen bonds) are energetically more favorable

42
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

than 180° reorientations about ('.., axes (breaking 1 VG7 oyer;

bonds) , the measured line shapes were analyzed to obtain hydrogen

1

° residence times * as a function of temperature. It was found

that for T<100K the line shapes are in agreement with either

(instantaneous) jump reorientations about a single C axis or random

reorientations about all four C axes. For T>100K, reorientations

about a single C_ axis are ruled out. Residence times derived for

C» reorientations about random axes range from 9.5 at 78K to 1.8 ps

at 150K. If Arrhenius behavior is assumed for the temperature

dependence of the residence time an activation energy of 2.26±0.25

12 -1

kJ/mol (0.54±0.06 kcal/mole) and a frequency factor of 3.7 x 10 s are obtained.

0.9 -

£

0.8

I

07

0.6

0.5

66 K • 78K

x I05K

a I30K

<j> A^ o I50K

T = 2 3ps / JX--- T = 265ps (90°C

2

)

/ /f\ X xV-r =3 4ps

/ /y ^\\

^ * RESOLUTION WIDTH

i

i

i

Q(A"

Figure 1. The full-widths at half-maximum (FWHM) of the measured

quasielastic neutron scattering spectra vs wave vector

transfer .for several temperatures. The solid lines are the

predictions of the C3~axis reorientation model for the

experimentally determined mean residence times. The

dashed line is the prediction of the 90°-C 2 reorientation

model with x adiusted to give the experimentally observed

FWHM at Q = 2.3A-1 for NH4CIO4 at 105 K. Estimated

uncertainties are shown.

43
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

To better characterize ammonium- ion dynamics in ammonium perchlorate,

higher resolution measurements of polycrystalline NH CIO^ and

single-crystal ND.C10, are in progress.

1. K. Skold, J. Chem. Phys . 49_, 2443 (1968).

2. H. J. Prask, S. F. Trevino and J. J. Rush, J. Chem. Phys. 62_,

4156 (1975).

POLARIZED RAMAN STUDY OF AMMONIUM PERCHLORATE

H. J. Prask

(Picatinny Arsenal, Dover, N. J.)

and

G. J. Rosasco

(Inorganic Materials Division)

The dynamical behavior of molecular groups in ammonium

perchlorate (AP) have been the subject of considerable interest for

1 2 some time. Recent work in this laboratory with neutrons has

considerably advanced the understanding of the NH, dynamics at low

temperature. In conjunction with this work we have examined the

temperature dependence of all Raman-active vibrations from 12 to 297K

in considerable detail, and a few modes to 500K.

The anomalous low-temperature behavior of certain B and

B_ lattice modes has been described previously. Recent work has

3g v been devoted to analysis and correlation of lattice and internal mode

behavior of AP and d-AP. Figure 1 illustrates changes observed in the

NH, internal modes in going from 32 to 297K. Similar changes do not occur in the CIO. internal modes.

4

General conclusions that can be drawn from the vibrational mode

analysis are as follows:

(1) The ammonium ions are bound in a very anharmonic and

anisotropic potential which leads to pronounced multiphonon scattering

44
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

1 '

X30

r i i

A

g

(X,X) 297K

1 '

X3

i

X30 <Jk_JL A„(X,X) 32K—^1^.

~\ 1 r~

&2g 297K

B 2 , 32K

1 ' 1 ' 1 ' 1

1 1 ' -1 '

XI * ^y \^__ B3

° 297K -A

B

3fl 32K XI

i 3200 2800 +

2400 2000 Figure 1. Polarized Raman spectra of the NH internal mode region

for single crystal NH.C10, at 32 and 297K.

4 4

16

2h

at high temperature and the anomalous broadening of a few lattice

3 modes at low temperature

;

(2) The structure inferred from the neutron dif f raction-1-

is consistent with Raman measurements and "selection rules" for D

symmetry in the 12 to 297K temperature range;

(3) Although no phase transition can be detected, both

external and NH. internal mode behavior indicates a gradual but

4 significant change in ammonium-ion dynamics in going from 12 to

^150K which is associated with NH, reorientations.

(4) Gradual softening of an A Q lattice mode is observed from

12K to 500K which is associated with the orthorhombic to cubic phase

transition at 513K.

1. C. S. Choi, H. J. Prask and E. Prince, J. Chem. Phys . 61_,

3523 (1974).

2. H. J. Prask, S. F. Trevino and J. J. Rush, J. Chem. Phys. 62_,

4156 (1975)

.

3. G. J. Rosasco and H. J. Prask, Sol. St. Comm. 16, 135 (1975);

NBS Tech. Note 860 (1975), p. 69.

45
INTERAGENCY AND UNIVERSITY COILABORATIVE PROGRAMS

LOW TEMPERATURE PHASE STABILITY OF AMMONIUM

NITRATE - POTASSIUM NITRATE SOLID SOLUTIONS

H. J. Prask, C. S. Choi, M. K. Farr and S. F. Trevino

(Picatinny Arsenal, Dover, N. J.)

Ammonium nitrate (AN) is, potentially, a very important

ingredient in munitions because of its "energetic" properties,

availability and relatively low cost. Its use, however, has been

impeded in part by the fact that a structural phase transition

(IV^III) occurs at 32 °C accompanied by a large change in density.

Temperature cycling through this phase transition leads to irreversible

expansion and cracking of cast fills. Addition of fractional amounts

of potassium nitrate (KN) to AN has been found to change the phase

diagram such that for 10%KN/90%AN (by weight), phase III is stable

from ^0 to ^45°C, eliminating the cycling problem at warmer temperatures

The low temperature phase stability is of equal practical importance

and this has been the subject of the present investigation.

Neutron diffraction has been used to determine the phase

transition behavior of 90%AN/10%KN as a function of time at a storage

temperature of -20°C. The results are summarized below:

(1) A phase transition (III-»V) occurs very gradually in

AN/KN "prills", cold-stored as received from the manufacturer;

(2) Indications of the occurrence of the transition begin

after ^5 days and it is not completed even after 35 days;

(3) The relative concentrations after 35 days of cold storage

are ^30% Phase III and 70% Phase V;

(4) Vacuum drying of the sample retards the phase transition

even further so that the first changes are observed only after

^25 days of cold-storage.

The practical conclusions to be drawn from this study are that

dried AN/KN might exhibit acceptable low-temperature storage stability;

however, "as received" samples do not. It appears that solid solutions

containing larger fractions of KN should also be investigated.

46
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

MODE GRUNEISEN PARAMETERS OF KBr

DETERMINED BY INELASTIC NEUTRON SCATTERING

M. K. Farr and S. F. Trevino

(Picatinny Arsenal, Dover, N. J.)

The room temperature acoustic phonon dispersion relations of

KBr at 1 bar and at 6,3 kbar have been measured using conventional

inelastic neutron scattering techniques. The mode Gruneisen

parameters, y(q,j), for the measured modes have been calculated from

the relation

Y(q

- i} = _ d ln "(q>.i) Ykq ' j; d In V

The relative volume changes was determined by measuring the change

in the lattice constant using Bragg scattering. Several calculations

of mode Gruneisen parameters have been made using various lattice

12 3 4 4 dynamics models. ' ' ' The breathing shell model (BSM) and anharmonic

3 deformation dipole model (ADD) calculations agree well with our acoustic mode measurements. Figure 1 shows the measured y(q,j)'s

together with curves calculated using the BSM.

CU'-T -

Figure 1. Mode Gruneisen parameters for acoustic modes in KBr.

Solid Lines are BSM calculations of Mitra et al. and

points are present measurements.

47
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

The y(q>j)'s f° r the optical modes of KBr are presently being

measured. Our preliminary results indicate that there may be

significant discrepancies between our measured y(q,j)'s and the model

predictions for these optical modes.

1. E. R. Cowley and R. A. Cowley, Proc . Roy. Soc . A292 , 209 (1966).

2. R. Ruppin and R. W. Roberts, Phys. Rev. B, _3> 1406 (1971).

3. R. J. Hardy and A. M. Karo, Phys. Rev. B, 7_, 4696 (1973).

/, S. S. Mitra and J. F. Vetelino, Private Communication.

HYDROGEN EMBRITTLEMENT IN TITANIUM

H. Alperin and J. Rhyne

(Naval Surface Weapons Center, White Oak, MD)

and

J. Rush

and

H. Flotow

(Argonne National Laboratory, Argonne, IL)

The phenomenon of hydrogen embrittlement of metals is well known

and various theories have been proposed to explain the results of macroscopic metallurgical experiments. What is lacking, however, is the

connection with the underlying microscopic behavior of the hydrogen in

the host metal lattice. Several important aspects of the embrittlement

process in titanium and its alloys are the role of stress, the solubility of hydrogen in the various phases and the diffusion of hydrogen

from site to site.

Neutron scattering techniques offer the possibility of answering

such questions as: Where in the host lattice do the hydrogen atoms

reside in the different crystallographic phases of the Ti-H system?

Does the site occupancy change with temperature? What are the activation

energies and jump times for the diffusion of hydrogen? How are these

characteristics affected by stress? Does the equilibrium phase diagram

48
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

of the Ti-H system accurately represent the actual non-equilibrium

situation as it exists in the metal?

Neutron diffraction measurements were performed to determine the

site occupancy of deuterium atoms in the a and $ phases which play an important role in the hydrogen embrittlement process. A special vacuum

furnace capable of temperatures to 900°C was built and used to measure

the site occupancy of deuterium in the a-phase of Ti D at 375°C.

The results show that the deuterium atoms are located approximately

68% on octahedral sites between the titanium atoms in their hexagonal

close packed lattice. The remainder of the deuterium atoms reside on tetrahedral sites. Ti D

n ^ in the B-phase at 400°C was also measured.

A discrepancy was observed between the equilibrium amount of y~phase

expected in the TiD _ 7 sample at room temperature and that actually

observed. This is attributed to a quenching of the a-phase when cooling

from high temperatures. This may be important for the embrittlement

process. The difficulty of achieving equilibrium was also shown in the

persistence of the lower temperature phases as the TiD„ , ? sample was

raised to higher temperatures.

CRITICAL AND LOW TEMPERATURE NEUTRON SCATTERING FROM

AMORPHOUS MAGNETS

H. A. Alperin, J. J. PJiyne and S. J. Pickart

(White Oak Laboratory, Naval Surface Weapons Center, White Oak, MD)

The investigation of the basic nature of the ferromagnetic

transition in an entirely new kind of magnetic material, namely

amorphous magnets has been extended to the compounds HoFe and

GdFe . This has been done in order to determine the generality of

the critical scattering results previously obtained on TbFe_ jn addition, the role of anisotropy in the rare earth ion has been

determined

.

49
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

The results on HoFe show that the scattered intensity has a Lorentzian shape as one approaches the Curie temperature (T ^ 195Ip

from higher temperatures. This yields a correlation length for the

i magnetic moment fluctuations which rise to a maximum value of only

^40A at T (in contrast to an infinite correlation range at T for

c - c a crystalline ferromagnet) and thus is similar to TbFe

9

. GdFe 9 also shows only a weak anomaly at T . We therefore conclude that

c for the rare earth amorphous ferromagnets in general, the critical

anomaly is weak and the spin .correlation length is finite at T . The giant, anomalous, small angle scattering observed to

increase with decreasing temperature below T in TbFe~ is also

seen now in HoFe~ . The present results however show that this effect

is missing in GdFe_ . This effect which we interpret as due to the

development of magnetic "grains" of size ^ 100 A or less now appears

to depend for its existence on an anisotropic magnetic rare earth

ion since it is present for neither YFe„ nor for GdFe

? (isotropic

s-state ion)

.

1. S.J. Pickart, J. J. Rhyne and H. A. Alperin, Phys . Rev. Letters 33 , 424, (1974).

SPIN WAVES IN AMORPHOUS Tb pe 2

J . J . Rhyne

(White Oak Laboratory, Naval Surface Weapons Center, White Oak, MD)

and

H. A. Mook

(Oak Ridge National Laboratory, ERDA, Oak Ridge, TN)

Using the Oak Ridge polarized beam time-of-flight spectrometer

discrete spin wave excitations were observed in amorphous TbFe~ at room temperature. Previous time-of-flight total scattering experiments

had revealed only a broad inelastic magnetic distribution at large wave vector, 0, characteristic of the magnon density of states, plus

50
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

(ED

TbFe 2 (AMORPHOUS)

Figure 1. Magnetic inelastic scattering in amorphous TbFe

? # ^he data were taken on the Oak Ridge polarized beam time-of-flight

spectrometer. The low dispersive branch is quadratic in

Q (see inset) and represents an~acoustic magnon with a weak

stiffness constant I) = 15 meV-A and evidence of a small

anisotropy energy gap.

a strong elastic component at low Q representing the anomalous

inhomogeneous magnetic structures (micro-domains averaging approximately

100 A) present in these materials. It was in fact the presence of

this large elastic scattering which obscurred the observation of the

expected long wavelength discrete spin waves and necessitated the use

of the polarized beam spectrometer. Only neutron spin-flip (magnetic

inelastic) scattering contributes to the scattering cross-section for

this technique. The resulting suppression of the elastic peak made

visible a dispersive acoustic magnon branch at low Q which is shown in

figure 1. This branch (quadrant in Q) corresponds to a very small spin

"2 wave stiffness constant D = 15 meV-A apparently due to the structural

disorder of the material and also shows evidence of a small (.25 meV)

anisotropy energy gap. An additional higher energy branch was also

observed as shown in the figure as well as a non-dispersive component

51
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

at approximately 9 meV energy transfer at large Q. It is planned to

study the temperature dependence of the low Q magnetic excitations in

this and other amorphous alloys using very fine energy resolution on

a triple axis spectrometer.

ANOMALOUS CUR IF TEMPERATURES OF RFe2 AMORPHOUS MATERIALS

J . J . Rhyne

(White Oak Laboratory, Naval Surface Weapons Center, White Oak, MD)

As part of a continuing study of the magnetization of the

amorphous rare earth-iron (RFe ) alloys, the alloys DyFe , HoFe , ErFe , and TmFe have been examined as a function of temperature

800

700

600

R-Fe

(CRYSTALLINE)

(BURZO)

(g-l)

2 J(J+l)

Figure 1. Curie temperatures of crystalline and amorphous RFe2

metals as a function of the DeGennes factor (see text)

Fundamental differences between the crystalline and

disordered materials are noted in particular the

vanishing of the amorphous T as the rare earth spins

a

c are removed

.

52
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

both above and below the Curie temperature. Dy, Ho, and Er alloys

are strongly ferromagnetic and exhibit the large "coercive" field

effects at low temperatures characteristic also of TbFe

?

. HoFe? exhibits significant time dependences in the magnetic properties at

low temperature. The Curie temperatures of the amorphous alloys

are suppressed below the corresponding crystalline compounds due to

the effect of the topological disorder on the exchange interactions.

This suppression in fact takes a very anomalous form as illustrated

in figure 1, which gives T as a function of the DeGennes factor for

the series of RFe ' materials in both crystalline and amorphous form.

The DeGennes factor is the projection of the effective rare earth

(only) spin and is the quantity to which the R-R and R-Fe exchange should

scale. The crystalline compounds show a 550 K background T from the

Fe-Fe interaction (i.e. YFe ?

) plus a montonic increase in T with

DeGennes factor as the rare earth exchange interactions become stronger.

In marked contrast, the amorphous materials show T vanishing smoothly

as the DeGennes factor goes to zero, implying the absence of the constant

background Fe-Fe exchange interaction in the highly disordered

amorphous alloys . The curie temperatures rises rapidly with increasing

rare earth spin and for GdFe and TbFe is sufficiently high to suggest

a feed-back or catalytic effect on the iron-iron exchange interaction

in the presence of strongly exchange-coupled rare earth spins. Such

a mechanism is peculiar to these amorphous materials and is being

investigated in detail.

1.. J. J. Rhyne, J. H. Schelleng, and N. C. Koon, Phys . Rev. BIO, 4672 (.974)

53
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

NEUTRON DIFFRACTION STUDIES ON TRANSITION-METAL SUBSTITUTED Fe Si

3

S. Pickart

(University of Rhode Island, Kingston, P.I a.nd Naval Surface Weapons Center, White Oak, MD)

and

T. Litrenta

(Fordhan University, New York, NY)

and

T. Burch and J. Budnick

(University of Connecticut, Storrs, CT)

Neutron diffraction studies were performed on Fe„ T Si, with

3-x x

T = Co, V and Mn and x < .06 in order to check the site preferences

inferred from earlier NMR spectra. The neutron studies were taken

on powdered and annealed samples with an external field of 8000 oe. applied along the scattering vector to eliminate magnetic scattering,

and the site populations derived from the structure factor ratio of

the first two superlattice lines. Large departures of this ratio from

unity indicate that V and Mn prefer the Fe site with 8 Fe near

neighbors, and Co that with 4 Fe and 4 Si n.n., thus confirming the

NMR results. The ratio for pure Fe.Si suggests a slight disorder

consisting of a preferential occupancy by Si of the first type of site.

1. T. Burch, T. Litrenta and J. Budnick, Phys . Rev. Lett. 33_> 421, (1974)

NEUTRON DIFFRACTION STUDIES OF BIOLOGICAL MATERIALS

J. C. Norvell and E. Prince

and

D. R. Davies

(National Institutes of Health)

A program to investigate the structure of biological materials,

utilizing the techniques of neutron diffraction was initiated at NBS at

the end of the fiscal year, in collaboration with the National Institutes

54
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

1 2 of Health. Recent neutron crystallographic studies of proteins ' and

low angle neutron studies of structures such as ribosomes, muscles, and

2 membranes have achieved some success at Brookhaven, Harwell and Grenoble.

In the former experiments, the positions of the hydrogen atoms and bound

water molecules are determined. Hydrogen atoms, which make up 1/2 of

the atoms in a protein, are vital to the folding and enzymatic function

of a protein, yet their positions cannot be determined from X-ray experiments. In the low angle work, large scale structural information is

obtained. The program at NBS will begin with crystallographic work on a protein: ribonuclease A, rubredoxin, and lysozyme being the most likely

candidates. Crystallization experiments are presently in progress, with

the assistance of Dr. David R. Davies, Laboratory of Molecular Biology,

NIAMDD, NIH. One of the main difficulties in protein neutron scattering

experiments is the relatively low neutron flux, resulting in slow data

acquisition rates. This should be greatly improved by the planned

development of a neutron protein crystallographic station with a position

sensitive detector.

L. Norvell, J. C. , Nunes, A. C. , and Schoenborn, B. P., Science, in

press

.

2. Brookhaven Symp. Biol. 27 , in press.

MOSSBAUER STUDIES ON DYSPROSIUMSCANDIUM AND AMORPHOUS DyFe

2 R. Abbundi and R. Segnan

(American University, Washington, DC)

and

D. Sweger

(Analytical Chemistry Division)

and

J . Rhyne

The NBS research reactor was used in this work to produce

periodically a Dy-161 Mossbauer effect source by irradiation of

55
INTERAGENCY AND UNIVERSITY COILABORATIVE PROGRAMS

GcLF . The following is a summary of the results from this project

on Dy-Sc alloys and on amorphous DyFe

?

.

a. Dysprosium-Scandium Alloys

Mossbauer measurements were made in a series of Dy-Sc alloys

ranging from 2% dysprosium to 75% dysprosium. In figure 1

is shown the Mossbauer spectra for the 10% dysprosium concentration.

All the measurements were taken at 4K. The 10% data clearly exhibit

a hyperfine splitting in the Mossbauer lines. In the 5% sample the

hyperfine pattern is not as clearly defined but it gives evidence of

split lines. From these data we conclude that a magnetic hyperfine

interaction exists for dysprosium concentrations above 5%.

Preliminary bulk magnetization measurements indicate that

the Dy-Sc system is not ferromagnetically ordered below about 25% of

2 dysprosium. Tentatively we can possibly explain the presence of

the hyperfine splitting of the Mossbauer spectra, as due to a local

magnetic ordering of the Dy moments in the immediate surroundings of

101 DY(.I0)SC(90) T = 4.2K DS2433

i H 1

1

|

| II 1 •

i i

• • •n %

• • >-IOO 1 Cj •> li mrL

••

z

7# H at ff V/\W \ m / J «B A 3 • 1

T • 2 7* iV\ T t 11 11 1 « J#

. 99 *\ / v IP i p ll •!/ i«J i >

\ A.JL • w \l ml

•I ^n mm 1 •• Jtf T K ^IjS * ' 1 1 " 1 < •\A •, • • T

_| j LU •%T «• f

cr A • 98 •

•

j i i i I

•

•L. 1 1 1 1_

.

-30 -20 -10 10 VELOCITY (CM/S)20 30

Figure 1. Mossbauer spectrum of DySc alloy - 10 at 90 dysprosium

T = 4.2K.

56
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

dysprosium atoms used as Mossbauer probes. Alternatively, a more exciting explanation is that relaxation phenomena are responsible

for the local ordering. Thus, the nuclear moment of a given dysprosium

atom experiences slow spin-spin and spin-lattice relaxation times and

therefore sees a slowly fluctuating hyperfine magnetic field. This

result is quite important because slow relaxation phenomena are not

normally expected in essentially metallic alloys.

100

LU

POLYCRYSTALLINE 300K

**V

•• • ? » • < *

?I00

4.2 K

HI 98

SPUTTERED 4.2 K

/ .

.i '

«

"•• V * .* . -

*•' :

*. •••

:" • •> •

•• •• A

V *

0*

<fj 100

q:

98

-20 -10 10 20

VELOCITY (CM/S)

Figure 2. Dy-161 Mossbauer spectra in poiycrystailine and amorphous

nvFo

57
INTERAGENCY AND UNIVERSITY COIIABORATIVE PROGRAMS

b . Amorphous DyFe~

Amorphous, magnetic, RE-TM metal alloys have now been prepared

3 4

at several laboratories and x-ray and neutron scattering studies in

sputtered TbFe

9 and GdFe? reveal a short-range atomic order significantly

different from that in their crystalline (Laves phase) counterparts.

Magnetization studies of amorphous TbFe~ have been described in terms

of a model in which the Dy spins are more strongly coupled to their

random-direction anisotropy axes than to the neighboring Fe spins.

This also accounts for the reduced magnetic moment per formula unit

compared with the corresponding crystalline alloy (RE and TM antialigned)

,

Previous Mossbauer studies have concentrated on the well-defined

electric field gradient (EFG) observed in the paramagnetic state

of amorphous REFe_ alloys which can be explained in terms of a dense random packed sphere model. This model yields an EFG at

TM sites and a magnetic anisotropy at RE sites both of which are nearly constant in magnitude but random in direction.

There have been no previous Mossbauer studies of either H .., ef f or QS for RE atoms in the amorphous REFe 9 alloys. In figure 2 are shown our Dy-161 spectra in polycrystalline DyFe„ at T = 4.2 K and

300 K and amorphous DyFe„ at 4.2 K. The magnetic hyperfine splitting

in the amorphous sample is completely collapsed at room temperature.

At 4.2 K the average H

ff=6.3 MOe , is about half-way between the value

err

2 for Dy metal and crystalline DyFe . The QS (e qQ/2) is 6 . 3 cm/s.

The outer lines of the amorphous spectrum are considerably broadened

while the central lines are not. This requires a distribution of

width AH __ (Dy-161) = 100 kOe at 4.2 K.

etr

The Dy-161 hyperfine fields were found to collapse very rapidly

with T/T and the spectral lines broadened by orders of magnitude

indicating a distribution of local exchanges.

We note that, whereas 12 Fe nearest neighbors surround Re atoms

in crystalline ReFe„ this number is reduced, on the average, to about

6.7 in the amorphous state. From our T = 4.2 K measurements we find

a reduction in Hgff (Dy-161) of 0.5 MOe and a reduction in e

2 qQ/2 of

58
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

about 2 cm/s in going from the crystalline to the amorphous state.

If we attribute the decreases in H .... to a change in the number of err nearest neighbors, we find that H _ is reduced by 75 kOe for each

Fe neighbor removed. On the other hand, if the decrease is due to

a reduction in (J

y

) > then < decrease in the Dy moment

.

a reduction in (J

7

) > then our results would imply a possible 6 percent

1. L. L. Isaacs, D. J. Lam and F. Y. Fradin, J. Appl. Phys . 42 , 1458 (1971).

2. J. J. Rhyne and R. Abbundi, private communication.

3. G. S. Cargill, AIP Conf. Proc . Series XVIII, 631 (1973).

4. J. J. Rhyne, S. J. Pickart and H. A. Alperin, Phys. Rev. Letters 29 , 1562 (1972).

5. J. J. Rhyne, J. H. Schelleng and N. C. Koon, Phys. Rev. B, 10_,

4672 (1974).

6. D. Sarkar, R. Segnan, E. K. Cornell, E. Callen, R. Harris,

M. Plischke and M. J. Zuckerman, Phys. Rev. Letters y2_, 542 (1974)

(and references contained therein)

.

7. G. J. Bowden, D. St. P. Bunbury, A. P. Guimares and R. E. Snyder,

J. Phys. C. (Proc. Phys. Soc.) 1, 1376 (1968).

SMALL ANGLE SCATTERING

C. S. Schneider

(U.S. Naval Academy, Annapolis, MD)

The prism refraction results for Ge, Cu, and (using a quartz prism)

have been reported for publication as b^ =8.1929(17) fm, b^ =7.689(6) fm

L>e Cu

and b =5.832(2) fm. The germanium amplitude agrees well with Shull's

o pendellbsung result; the copper value is higher precision in agreement

and the oxygen value is higher precision standing 5a away from previous

2 results.

59
INTERAGENCY AND UNIVERSITY COIIABORATIVE PROGRAMS

The small angle scattering diff Tactometer has been Installed at BT-3

This raised beam Instrument, has one axis tipping on the I i rst crystal

and two axis tipping plus translation on the second crystal yielding a

5 2

° flux of roughly 3x10 n/cm s of Be filtered 4.0A neutrons using a pair

of 3° mosaic pyrolytic graphite crystals to extract the beam. The

intensity passed through the following horizontal pair of silicon

4 crystals (50 second mosaic) is 6x10 n/min which should be slightly

improved when higher quality graphite crystals are used. A pair of

germanium crystals have been prepared for a three-bounce (111) Bonse4 Hart reflection and should yield about 10 n/min over the Darwin width

with a sixth power angular tail decrease. This dif f ractometer can then

resolve spherical defects well above one micron in size.

The procedure for data inversion of this nearly infinite slit

3 height system by Mellin transform has been computerized and studies

have been completed on the "ringing" of defect density results due to

upper and lower truncation of the data range and finite step size. A

first application of the system will not involve inversion of intensity

profiles but rather variation of intensity scattered at a fixed angle

due to a Christiansen filter containing U-235 0„ powder. This is a

4 variation on the excellent technique developed in Germany during this

decade.

1. C. G. Shull and W. M. Shaw, Zeit. fur Naturforschung, 28, 657-661

(1973).

2. R. E. Donaldson, L. Passell, W. Bartolini and D. Groves, Phys. Rev.

138B, 1116-1119 (1965).

3. J. Riseman, Acta Cryst. 5_, 193-196 (1951).

4. L. Koester and K. Knopf, Zeit. fur Naturforschung3 27a , 901 (1972).

60
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

A DIFFRACTION STUDY 0^ AMORPHOUS MATERIALS

G. A. Ferguson, J. H. Konnert and J. Karle

(Naval Research Laboratory, Washington, DC)

The neutron and x-ray diffraction technique has been employed

to study vitreous samples of Si0 o , Ge0o , KAlSi„0 o and NaAISi o The information obtainable from analysis of these diffraction data is

the distribution of interatomic distances expressed in the form of

a radial distribution function. Details of the newly developed data

reduction procedures which have yielded heretofore unseen detail

in the radial distribution function for vitreous samples have been

published elsewhere (1,2,3,4). The results obtained for silica (SiO_)

and germani (GeO ) , given in figure 1, show significant deviations from

a. uniform distribution of interatomic distances out to approximately

o 20 A. The consequence of this evidence is that appreciably greater

ordering exists than has been previously reported for these vitreous

systems (5,6). Furthermore, serious doubt is raised that such systems

can be accurately described by a continuous network of individual

tetrahedra connected together randomly and restricted only by the

steric hindrance of the local environment with prescribed bond angle

limitations (5)

.

Glasses of the composition NaAlSi

?0_ and KAlSi Q p have been

investigated. The radial distribution functions for these materials

indicate that the basic structure of silica glass is preserved in

these glasses. The Al atoms replace some of the Si atoms at the centers

of the silicate tetrahedra and the Na and K atoms fill in the

interstices in the network. Studies of the macroscopic properties

of solid solutions of these glasses have revealed that they are closely

related structurally. In order to estimate the extent to which the

NaAlSi o and KALSi„0 n glasses are isostructural, neutron diffraction

3 j 3 8

experiments were performed. Since the neutron scattering factors for

Na and K are nearly identical (0.35 x 101 cm and 0.351 x 10 cm

respectively) it is expected that similar radial distribution functions

61
INTERAGENCY AND UNIVERSITY COIIABORATIVE PROGRAMS

O 5 ' 10 15 20

Figure i. Radial distribution functions for silica and germania

NEUTRON DATA

KAI5i

3Oa

Figure 2. Radial distribution functions from neutron scattering for

KAISi o o and NaAlSi.0 o i o •> o

62
INTERAGENCY AND UNIVERSITY COIIABORATIVE PROGRAMS

would be obtained. The distribution functions obtained are given

in figure 2 . It is seen that the results for both glasses are

o comparable in the region 0<r<12 A. Beyond this point the maxima and

minima are seen to occur at approximately the same r-values although

those for NaAlSi o o damp rapidly. This result implies that the

structure of the NaAISi o and RAlSi„0 glasses are similar, but the jo- jo

KAISi o is somewhat more ordered, perhaps as a consequence of the

3 o presence of the larger K ion.

APPLICATION OF ROBUST/RES I STANT TECHNIQUES TO CRYSTAL

STRUCTURE REFINEMENT

E. Prince

and

W. L. Nicholson

(Battelle Pacific Northwest Laboratories, Richland, WA)

A technique for fitting a theoretical model to a set of experimental

data points, and estimating the best values of adjustable parameters in

the model, is said to be "robust" if it is applicable for a broad class

of distributions for the errors in experimental data, and "resistant" if

the estimates are not highly dependent on any small subset of the experimental data. The method of least squares, the method most commonly used

for refining crystal structures, possesses neither of these properties.

Least squares is an excellent fitting technique for normally distributed

errors. With broad tailed error distributions and/or the presence of a few bad data points in a large data set least squares can give anomalous

results. In recent years statisticians have been developing methods of

fitting and parameter estimation which work nearly as well as least

squares for ideal data sets but which are robust and resistant.

The method of least-squares is based on finding the minimum value

9 of the quantity yw.(y. -y . ) , where y. is the value of an observ-d data H J h l

; io 7 ic io

point, y. is a calculated value of that point based on some theoretical

63
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

function containing adjustable parameters, and w. is a weight. For the

, X. , , , 2 metnod to work: well the weight, w., must be proportxonai to l/a. , 2 X 1 where a. is the variance of the observation y. . This variance is,

1 10

however, usually not known a priori, but is approximated by a formula

containing a term arising from an assumed Poisson distribution of random

counts and one or more other terms which estimate additional experimental

error associated with the observed value, y. . "Robust" implies an

xo insensLtivity to small errors in this approximation spread over the

entire data set, whereas "resistant" implies an insensitivity to the

presence of a small subset in which the variance is grossly underestimated

The response of a refinement technique may be modified by adjusting

the weights according to the formula like w'=wW(x), where x=(y -y )/Ka ,

' io ic i a. is the standard deviation approximated as described above, and K is a

1 constant. The function W(x) will be called a W-function. Tukey has

described certain characteristics a W-function should have in order to

make the refinement procedure robust/resistant. For small values of x the procedure should closely resemble least-squares. For large values

of x, that data point should be ignored, which means W(x)=0 for large x. In between the function should fill in smoothly. We can express these

conditions mathematically by the following stipulations:

1. W(x)=W(-x). (The function is even in x.)

2. W(0)=1.

3. W'(0)=0.

4. W(X)=0, |x|> 1.

5. W' (1)=0 (Many W functions don't have this property).

6. W

1 (x)<0, 0<x<l.

2 The crystallographies least-squares program RFINE has been modified

4 6 I I to include, as an option, a W-function of the form W(x)=l-3x +2x (|xj<L),

which, in addition to the conditions above, satisfies an additional con- dition W" (0)=0. This function has been used in several refinements in

which there was initial difficulty in getting the structure to converge.

64
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

In particular, the data set for lead deuterium orthophosphate J was studied in some detail in order to determine an appropriate value for

the constant, K, which appears tin the W function. Good results were

obtained by setting K=3.5R , where R is the "Interquartile range," the

q q

n ° ' range of values of AF./a. which includes the middle half of the data.

It should be noted that for an "ideal" data set, with normally distributed

errors, R /1.348 is an unbiased estimate of a, the estimated standard

deviation of an observation of unit weight. Therefore with such a data

set the W-function will alter the weights for more than 97% of the data

by less than 9%.

The robust/resistant methods will be used to repeat the refinements

of the structure of D(+)-tartaric acid originally carried out by

4 Hamilton and Abrahams as part of the single-crystal intensity project

of the International Union of Crystallography. We hope to determine

whether the differences in refined parameters found in that project,

some of which were rather large, can be reduced by application of

robust/resistant methods.

1. J. W. Tukey in Critical Evaluation of Chemical and Physical

Structural Information, National Academy of Sciences, Washington,

DC, 1974.

2. L. W. Finger and E. Prince, NBS Tech. Note 854 (1975).

3. C. S. Brickenkamp and E. Prince, NBS Tech. Note 860, p. 55 (1975)

4. W. C. Hamilton and S. C. Abrahams, Acta. Cryct., A26 , 18, (1970).

BT-4 THREE AXIS NEUTRON SPECTROMETER

A. Cinquepalma, W. Rymes, A. Tudgay, J. M. Rowe, J. J. Rush

and

H. Prask and S. Trevino

(Picatinny Arsenal, Dover, NJ)

This three axis neutron spectrometer is now in operation. Preliminary

calibration experiments show that the flux at the sample is ^10 neutrons

2 per cm per second at an energy of 14 meV with an energy resolution

65
INTERAGENCY AND UNIVERSITY COIIABORATIVE PROGRAMS

r o of ^12%, and 3x10 neutrons per cm per second at an energy of 14 meV

with an energy resolution of ^WL.

Initially, the spectrometer will employ one complete analyzer

system, rather than the two systems which were designed and manufactured

for it.

It was decided that the benefits to be derived from the improvement

of the BT-6 three axis spectrometer by the installation of this new

analyzer far outweighed its use as an anti-parallel analyzer on the BT-4

machine at this time. The anti-parallel arm, with its motor and drive

system, is installed and ready to accept another analyzer in the future.

The final shielding configuration which includes a traveling beam

stop, allows unrestricted changes of 28 from 20° to 79°, or from 35° to

94°. Either of these ranges may be selected by the insertion or removal

of one readily accessible shield and the relocation of two limit switches

and stops.

The safey systems which have been incorporated into this spectrometer

include; mechanical latches which prevent the dropping, through electrical

or pneumatic malfunction, of any of eight traveling shutter segments

that are capable of rotating out from behind the saddle shield; a latch

"scram" circuit which senses any traveling shutter segment which is not

latched "up;" and dual gamma sensing meters, with set point interlocks,

located at the edge of the saddle shield in order to sense the approach

of a "down" shutter segment. The latch "scram" interlock and the re- dundant gamma interlocks form an AND gate. Loss of any of these contact

closures, or loss of line power, causes immediate closure of the inlet

beam shutter, which is raised pneumatically only when a spring return

air solenoid valve is powered "on."

66
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

A HIGH PRESSURE SYSTEM TO NEUTRON DIFFRACTION

M. K. Farr, S. F. Trevino , and IT. J. Prask

(Picatirmy Arsenal, Dover, N. J.)

and

W. B. Daniels

(U. of Delaware, Newark, Del.)

A high pressure system for use in various neutron diffraction

experiments has been completed . The system is capable of generating

hydrostatis pressures up to 7 kbars at room temperature in the present

aluminum sample cell. The cell can be mounted on a conventional

neutron dif f Tactometer or triple axis spectrometer.

The system consists of a 10 kbar handpump connected to an aluminum sample cell via a stainless steel capillary tube. A

fluorocarbon fluid is used as the pressure transmitting liquid.

A manganin manometer is incorporated into the pump body to monitor

the pressure.

The observed loss in intensity due to the cell and fluid is

only 25-30%. The high pressure system could be used up to 10 kbar

with a proposed steel cell but the loss in intensity would be

60-70%.

1. W. B. Daniels, Rev. Sci. Instr. 37_, 1502 (1966).

67
D. Non-RRD NBS Programs

activation Analysis: simiary of ! 975 activities

Harry L. Rook

(Analytical Chemistry Division)

The Activation Analysis Section has twelve full time employees

located in the NBS Reactor facility. Of these employees, eight are research scientists, three are technical support personnel and one is on sabbatical leave from Washington State University.

The Activation Analysis Section, in support of the Analytical

Chemistry Division, conducts research and analyses in four basic program

areas

.

Basic Research in 1'uclear Analytical Chemistry

This activity is primarily aimed at improving the analytical

measurement system using nuclear techniques. This includes analytical

method development, improvement in radiochemical separation schemes, and

all relevant areas of analytical quantitation. The end result of this

activity is to have a constantly expanding analytical capability which

can be applied to all areas of elemental analysis.

Analytical Research Applied to Specific Programs

This activity utilizes the section's analytical capability to

provide reliable analytical data in the study of systems dependent on trace element composition. Many programs in materials research, environmental studies, and clinical chemistry require a complete understanding of trace element composition in order to define their role in

the system under study. The analytical data provided by the Activation

Analysis Section combined with that of other analytical techniques

provide this essential information.

68
NON-RRD NBS PROGRAMS

Analytical Support for the SRM Program

Analyses performed on new Standard Reference Materials (SRM's) are

an extremely important area of the section's activity. Extreme emphasis

is placed on the accuracy of analytical results. Confidence in results

provided by the Activation Analysis Section has been built over many

years of careful work and every effort is expended to maintain and build

on this confidence.

Service Analysis

Service analyses are a small but important part of the section's

analytical program. As a general rule, service analyses are only

undertaken when the analytical capability cannot be conveniently obtained by a commercial laboratory or when the analysis will expedite an NBS program. There are many cases where, in conjunction with other

techniques of the Analytical Chemistry Division, a unique measurement

has been made. This is especially true where highly accurate results

are of prime importance.

Summaries of the work completed this year in the four basic

program areas will be included. More detailed descriptions of specific

projects can be obtained from literature references or individual

program reports.

1. Basic Research in Nuclear Analytical Chemistry

a. Instrumental Neutron Activation Analysis

R. M. Lind strom and H. L. Rook

For the determination of many elements in suitable matrices by

neutron activation, radiochemistry is not always required. In the most

favorable cases it is only necessary to irradiate samples and appropriate

standards and to assay the resulting radioactivity with high-resolution

69
NON-RRD NBS PROGRAMS

semi-conductor gamma detectors. Savings in time and effort, especially

for routine analyses, are considerable once the method has been developed to be of the desired level of reliability. Considerable effort

has been expended in the past year to provide this reliability.

The equipment required for this type of analysis, in addition to

the NBSR, consists of Ge(Li) detectors coupled with means for automatic

and accurate positioning of samples, multichannel pulse-height analyzers

with live-time and time-of-day clocks, and magnetic tape data recorders.

A crucial operation in any instrumental analysis is the reduction

of raw spectral data into final analytical results. The analyst, in

cooperation with his surrogate, the computer, is required to make

judgments on the qualitative and quantitative suitability of the data

and must choose the best of several possible means of analyzing the

information at hand. For our spectra, which usually contain 4096 sixdigit numbers from which dozens of peak areas and positions must be

extracted, a large computer program is indispensable. Spectral data are processed at the NBS Computer Science Center by the computer code QLN1,

developed on contract by H. Yule (NUS Corporation) for this purpose.

The program performs extensive qualitative analysis of the data for the

identification of peak characteristics of the isotopes sought. The

quantitative comparison of the appropriate peak areas in samples and

standards to arrive at elemental concentration and error estimates are performed for specified element following qualitative analysis. This

code is in a continual process of refinement, but for well-resolved

peaks the reproducibility and accuracy are excellent, and clearly

superior to hand calculations. Much attention must still be paid by

the analyst to the quality of the input data to the program. However,

this essential feature of the instrumental analytical process is common

to all methods of spectral data analysis.

The instrumental analysis process has been applied extensively to

date in the LESL Headlight Glass Program,, in the analysis of new biological Standard Reference Materials, and in several smaller sets of

70
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service analyses. Standard conditions of irradiation and counting are

in the process of definition in order to remove the present requirements

that standards be irradiated anew for each new unknown sample in routine

service analysis. To date eight elements (As, Cd, CI, Cr, Cn, K, Mn,

and Na) have defined standard sensitivities.

b. The Determination of Iodine-129 at Natural Levels

H. L. Rook, J. E. Suddueth and D. A. Becker

Iodine-129 levels have been determined and reported in biological

materials that naturally accumulate iodine, such as animal thyroid and

kelp. However, published procedures have insufficient sensitivity to

determine 1-129 in other environmental and biological matrices. This

work was undertaken to demonstrate the feasibility of using a mass separator to lower the detection limit for the determination of 1-129.

It can be calculated that if 1-130 is separated free of other radioactivity , less than 10 lL{ gram of 1-129 can be detected using low level

B~Y coincidence sum counting techniques. Mass separation is an extremely important tool as it can ^e the only means of separating 1-130 from

other iodine isotopes in the irradiation products. This fact, plus the

virtual elimination of other radioacitve contaminants such as Br-82,

accounts for the improved sensitivity.

In this project, the total analytical procedure for the quantitative analysis of 1-129 was reviewed and improved wherever possible:

a revised preseparation of total iodine was developed

based on a sample combustion and quantitative isolation

of iodine.

a substantial reduction of system blank was demonstrated

by preirradiation operation in a Class 100 clean

room;

design changes were made on the mass separator which

resulted in substantially improved yields;

71
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the mass separator operation was optimized and data were obtained on yields, intermass contamination and

memory;

an improved procedure for 3~Y coincidence counting

was devised where the 1-130 was directly implanted

into 3 scintillator material;

finally, real samples were run to give realistic

estimates of the detection limit, blank level and

its variations, and levels of 1-129 in selected

environmental matrices.

With all of the individual components of the analytical scheme

worked out and tested with tracers, analyses were conducted for 1-129

content of two natural samples. One sample was a freeze-dried hog

thyroid, obtained from the U.S. Department of Agriculture, which

represented samples naturally enriched in total iodine. The second was

a freeze-dried, filleted albacore tuna fish sample, which is currently

being developed at NBS as a trace element research material and on which

numerous trace element studies have been conducted.

Initial analyses were carried out in a specially cleaned fume hood

in a normal working laboratory area. One run each was carried out on the hog thyroid and tuna fish. The analyses were preceded and followed

by blank runs where the entire procedure was carried out with empty,

cleaned equipment (boats, combustion tubes, charcoal traps, etc.). The

results are shown in table 1. As can be seen from the blanks with their

associated variability, the system blank was the major limitation on the

analytical system. One problem was that 1-129 standard solutions which

were many orders of magnitude higher than normal levels, had been

prepared in an adjacent laboratory area and thus contamination of the

entire laboratory area was possible.

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Table 1. System Blank for Normal Laboratory Operation

Concentration,

Sample Wt sample, g g I-129/g sample

Blank =1.0 2.2 x 10~ lu

Tuna 0.973 1.7 x 10~ n

Hog Thyroid 2.131 4.2 x 10~ n

Blank = 1.0 2.5 x 10~ n

In light of the severe blank problem, the entire sample preparation and

preseparation apparatus was cleaned and moved in a Class 100 clean room. All sample manipulations were carried out in the clean room. Only after

the preseparated samples were sealed in quartz were they removed from

the clean room facility.

Analysis on the hog thyroid and tuna standard were repeated and a significant reduction in blank was observed. The results are given in

table 2. As can be seen, blank levels were reduced by almost three

orders of magnitude by adopting clean room operation. These blank

levels were limited by variations in background counting statistics and

thus could be lowered by subjecting the samples to higher neutron doses.

For these samples, however, that was not necessary. The samples con- tained significant activity above background levels. These analyses,

although limited in number, have conclusively demonstrated the ability

of determining as little as 10 8 total atoms of 1-129 in real biological

matrices. This sensitivity is extremely important if samples of biological origin, other than iodine concentrators such as kelp and thyroid,

are to be analyzed.

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Table 2. 1-129 Analytical Results

Concentration,

Sample Wt sample, g g 1-12 9 /b sample

Blank =1.0 8.5 x 10~ 1I+

Hog Thyroid 1.91 9.0 x 10" 12

Tuna 1.22 9.3 x 10~ 13

Tuna 1.53 7.9 x 10~ 13

Blank =1.0 4.5 x 10~ 14

More detailed information on this work was published in Analytical

Chemistry, 47, 1557 (1975).

c. Thorium Determination in Glass by the Nuclear Track Technique

B. S. Carpenter and G. M. Reimer

The Nuclear Track Technique has been applied for the determination

of thorium in glasses. Two irradiations were performed. The first was with a thermalized flux to determine the uranium content via fission of

U-235. The second irradiation was with a fast flux to induce the

fission of thorium, in addition to uranium. By comparing track densities

of both irradiations to a uranium standard, the "track excess" of the

second irradiation was related to the thorium content. The accuracy was dependent on the Th/U ratio. The uncertainty for the Th/U ratio of 4 was approximately 20 percent and increased as the ratio decreased.

Results obtained by this procedure on various samples and standard

materials are given in table 1.

A complete account of this work was published in Nature, 247 , 101,

(1974).

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Table 1. Thorium and Uranium Content by Nuclear Track Analysis

Th (ppm bX

U (ppm by U isotopic Th (ether densit

weight)" weight) ratio 8/5 mei:hod, ppm g/cm 3 Sample by weight)

La 1 87±7 0.015

b natural 76° 3.60

La 2 265+33 d ii - 3.56

La 3 466±56 0.015

b '° ii 462° 3.58

La 4 712±60 _d ii - 3.61

La 5 920±65

d ii - 3.55

T-l 31.5±1 .0 0.046 189 31°

40.6 8

2.28

K2a 0.42±(3.04 0.345

e ' f natural 0.352

f

2.03

614 SRM

b c 0.823 ' 387 0.746° 2.55

a errors are 1 standard deviation based on track counting statistics

b nuclear track determination

c isotopic dilution mass spectrometry

d since all the lanthanum glasses were made from the same base melt,

it was assumed that the U content did not vary for the series of

glasses

e X-ray fluorescence

f neutron activation analysis

g using a irradiation, see reference (10)

d. Selective Radiochemical Separation of Chromium

L. T. McClendon

Chromium has now been identified as a essential trace element in

human nutrition. Conversely at high concentrations, or in different

chemical states, it can cause deleterious or toxic effects. There is

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thus a definite need for reliable methods of analysis for chromium at

the trace level. A recent laboratory intercomparison of fossil fuels

(coal, fly ash, fuel oil), which was conducted jointly by the Environmental Protection Agency and the National Bureau of Standards pointed up

the unfortunate state of chromium determinations as performed by most of

the analytical community. Three standard analytical techniques were

used in the intercomparison, atomic absorption, emission spectrometry,

and activation analysis. Of the twenty-two laboratories which reported

results for chromium in fly ash only two were within the NBS recommended

value of 131 ± 2 pg/g. The others ranged from 21 ug/g to 289 ug/g, with

no discernible pattern. As a result of these round robin analyses, and

other similar analytical discrepancies, it has become evident that more

biological and environmental materials needed to be studied and certified for their chromium content.

When conducting NAA on samples containing less than one ug/g

chromium, a radiochemical separation is almost obligatory to optimize

the sensitivity and to eliminate interferences.

A destructive NAA technique, using tribenzylamine-chloroform

solution to extract chromium, was developed at NBS and used to determine

the chromium content in five materials—fly ash, coal, orchard leaves,

urine, and bovine liver. This technique involves four basic steps: (1)

irradiation; (2) dissolution with HCIO4-HNO3 mixture; (3) extraction of

Cr VI with a 1% tribenzylamine-chloroform solution; and (4) counting the

activity of the 320 keV y -ray of Cr-51. Tables 1-3 show the results

obtained in fly ash, coal and orchard leaves using this technique.

This method is selective for Cr VI, thus for samples not requiring

processing which might alter the oxidation state of the chromium this

technique could allow determination of the relative amounts of Cr (III)

and Cr (VI) in the sample.

A complete description of this work was published in Trace

Substances in Environmental Health, VIII, (1974), D. D. Hemphill, Ed.,

University of Missouri, Columbia p. 255-257.

76
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Table 1. Concentration of Chromium in Fly Ash

Sample // Ug/i

132.8

132.1

131.2

132.6

132.3

132.7

X = 132.3 ± 0.35*

Recommended Value 131 ± 2 yg/g

* Error expressed as ts at the 95%

confidence

level

.

Table 2. Concentration of Chromium in Coal

Sample # ^g/g

19.28

20.35

20.44

20.29

19.57

21.06

X = 20.17 ± 0.76*

Recommended Value

20.2 ± 0.5 ug/g

* Error expressed as ts at the

95% confidence

level.

/n

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Table 3. Concentration of Chromium in Orchard Leaves

Sample # pg/g

1 2.490

2 2.472

3 2.410

4 2.447

5 2.484

6 2.433

7 2.463

8 2.481

X = 2.460 ± 0.025*

Recommended Value

2.6 ± 0.2 pg/g

* Error expressed as ts at the

95% confidence

level.

e. A Spontaneous Deposition Radiochemical Separation for

Platinum Determination in Biological Materials

D. A. Becker, P. D. LaFleur, and A. LeRoy

The spontaneous deposition technique has been used a number of

times for radiochemical separations in activation analysis (1, 2). It

has also been used as a preirradiation chemical separation method (3)

.

Although this technique has been used for the analysis of one or more noble metals from inorganic materials (2) and metals (3), this technique

apparently has not been applied to the determination of the noble metals

in biological materials.

The use of platinum and possibly other noble metals in motor vehicle

emission control systems has recently been implemented. It thus becomes
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imperative that accurate and sensitive methods for the determination of

these elements be available for the evaluation of environmental baseline

levels and any real or imagined increases in these levels.

The method developed is capable of quantitatively determining

gold, platinum and palladium in a wide variety of biological and environmental matrices. This technique is also currently being evaluated for

possible use in the determination of additional noble metals simultaneously.

The analytical procedure entails wet-ashing with nitric-perchloric

acids with carriers (including copper holdback carrier) , redissolving

the residue in aqua regia, and then plating out a silver metal powder.

The removal of the noble metals can be accomplished using either the

batch method, or by passing through a column of the silver particles

suspended on cellulose or asbestos fibers.

Tracer studies made using this procedure showed quantitative

recovery (>99.5%) for the AU-198, AU-199, and PD-109, for both the batch

and the column methods.

The application of this technique to biological samples at first

resulted in radioactive contamination of the silver powder with Cu-64

radioisotope. Subsequent modification of the technique to use copper

holdback carrier and an ammonium hydroxide wash reduced this copper

radioactivity to negligible levels.

This analytical system has been applied to the determination of

gold, platinum and palladium in several biological materials.

Preliminary results on the analyses of animal tissue and botanical

samples gave 1.8 and 0.2 ng/g for gold, <15 and <9 ng/g for platinum,

respectively, while all palladium results were <1 ng/g. These analyses

were made using a neutron flux of 5xl0 13 n-cm i[ s

l for 1 hour, and

counting on a 16% efficient Ge(Li) detector or LEPS system.

The results of this work are being presented at the 1975 International Nuclear and Atomic Activation Analysis Conference held in

Gatlinburg, Tennessee.

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f. The Simultaneous Determination of Tellurium and Uranium

E. S. Gladney and H. L. Rook

Tellurium and uranium have not been shown to play essential roles

in the trace element biochemistry of higher animals. Rather, both

elements are potent biotoxins. Information on the toxicology of tellurium

is limited, but it is believed to resemble arsenic more than selenium in

its toxic action. Tellurium binds uniformly to soluble proteins in the

blood, has been implicated in nerve and brain damage in rats, and is

readily transported across the placental barrier. Reduction in general

activity and in longevity has been demonstrated in mice fed sub-toxic

doses of tellurium in water, but no influence on carcinogenicity or on the production of other tumor types was observed. No other data appear

to have been accumulated regarding the effects of long-term low-level

exposures of tellurium to mammals.

The toxicology of uranium has been extensively investigated. In

addition to the radiation hazard, the ingestion of uranium and its

compounds has been implicated in arterial, kidney, and liver damage.

Few analytical techniques have the demonstrated sensitivity to

permit the study of tellurium in biological and environmental materials

at naturally occurring levels.

Atomic absorption spectrometry has been utilized to determine

tellurium, generally above the yg/g concentration level , but again this

technique does not have the sensitivity necessary to determine tellurium

in most biological and environmental matrices without a pre-concentration

step.

In this work, both tellurium and uranium were analyzed using a combustion method followed by gas phase separation of iodine-130, a decay product of tellurium-130. The procedure was adapted from a separation originally developed for the determination of mercury. Four

principal advantages over currently used techniques have been attained.

This procedure requires a minimum of chemical manipulations, thereby

80
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reducing the chances of technique related errors; the separation of

radioiodine is quantitative, eliminating the need for chemical yield

determinations; the procedure can be utilized with a variety of matrices

without modification; and the low limits of detection, especially for

tellurium, permit the characterizations of these elements at their

naturally occurring levels. Even though the use of iodine fission

products for the determination of uranium is itself not new, the com- bustion technique provides a rapid, extremely sensitive method for

measuring uranium simultaneously with tellurium.

Using the analytical procedure developed, the tellurium and

uranium concentrations in three NBS Standard Reference Materials were

determined. These materials were: SRM 1517 Orchard Leaves, SRM 1632

Trace Elements in Coal, and SRM 1633 Trace Elements in Fly Ash. The

individual results are given in tables 1 and 2, alonR with the NBS

certified values for the uranium concentrations. It was assumed that

the uranium in the SRM's had the natural isotopic abundance. The results

compare well with the certified values established by the other analytical

techniques.

The confirmed accuracies of the uranium values obtained by this

procedure (table 1) are of vital importance in confirming the reliability

of the tellurium analyses. Even though tracer studies using 1-125 were

run to demonstrate that the separation was quantitative, the accurate

uranium results indicated that the iodine separation was in fact quantitative when using real samples. By inference, one may assume that the

tellurium results are also accurate, since any errors in the iodine

chemistry would have been reflected in the results of the simultaneously

determined uranium.

81
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Table 1. Uranium Concentrations of Standard Reference

Materials, yg/g

SRM 1571

0.0217

0.0244

0.0247

0.0319

0.0185

0.0300

0.0254

Mean 0.025

a

s 0.004

NBS

certif

:

ied

value 0.027 ± a

SRM 1632 SRM 1633

0.99 9.7

1.17 11.9

0.95 12.5

1.13 14.3

1.14 12.3

1.08 9.5

1.07 14.8

1.1 12.1

0.08 2.0

0.003 1.4 ± 0.1 11.6 ± 0.2

s is the standard deviation of a single determinationTable 2. Tellurium Concentrations of Standard Reference

Materials, Mg/g

SRM 1633

9.5

9.9

12.1

9.9

9.0

9.1

Mean 0.011 0.60 9.9

sa 0.003 0.04 1.1

PL s is the standard deviation of a single determination

82

SRM 1571 SRM 1632

0.012 0.56

0.017 0.66

0.007 0.61

0.010 0.60

0.011 0.62

0.008 0.54
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This analytical procedure has also been used to measure the

tellurium and uranium concentrations on atmospheric particulates

collected in rural, southeastern Maryland during August 1973. The

sensitivity of this technique permitted these elements to be measured on particulates from less than 40 m of air. The concentrations of tellurium,

uranium and aluminum for four different days sampling are reported in

table 3. The aluminum concentrations were measured by non-destructive

instrumental neutron activation analysis.

Table 3. Uranium and Tellurium Concentrations on Atmospheric Particulates

Sample date

[Al]

ng/g 3 [U]

pg/m 3 U EF

a

[Te]

pg/m 3 [Te EF

a

] x

lO'4

14 Aug. 1973 400 39.7 2.2 260 2.5

15 Aug. 1973 280 28.9 2.3 390 5.4

16 Aug. 1973 1440 110 1.7 520 1.4 23-24

23/

24 Aug. 1973 510 49.3 2.1 290 2.2

aEF = Enrichment Factor relative to Wedephol's Crustal Average.

All data have been corrected for filter blank. Atmospheric

enrichment factors (EF) for tellurium and uranium, relative to Wedepohl's

crustal averages, have been calculated using the method of Gordon and

Zoller. The low uranium EF's indicate that the airborne uranium was probably of crustal origin. The high tellurium EF's suggest a strong,

non-crustal source for this trace metal in the atmosphere. Similar high

EF's have also been observed for selenium in a variety of environmental

measurements

.

The high EF's for these chemically similar elements suggest

either poorly established crustal levels, an important natural non- crustal source, or anthropomorphic pollution. The tellurium results are comparable with the only previously reported atmospheric measurement of

83
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<0.8 ng/m 3 in College Park, Maryland.

A complete description of this work has been published in Anal.

Chem. 3 47, 1554, (1975).

g. Fission-Track Determination of Uranium in Solutions

B. S. Carpenter, G. M. Reimer, and R. Z. Zielinski

A fission-track procedure which permits the routine determination

of <1.0 part-per-million uranium concentrations in solutions has been

developed. As little as 1.0 ml of sample or standard is required. The

solution is placed in polyethylene tubing or a snap-cap vial. A track

detector is submerged; the container is heat sealed and irradiated with

thermal neutrons to induce fission of uranium-235. Detectors are lowuranium plastics or fused quartz platelets, the selection depending on

the nature of the sample and the irradiation conditions. After irradiation, the detectors are removed and chemically etched, and the enlarged

tracks are counted with an optical microscope. The concentration of

uranium is proportional to track densities and can be determined in a unknown by comparing track densities in its detector to track densities

in the detector of a standard solution, providing the irradiation

conditions were identical. Total uranium is determined by consideration

of the uranium isotopic ratio which can be regarded as natural for most

solutions

.

Present sensitivity of the method allows determination of uranium

concentrations of 10 yg per liter with an estimated coefficent of

variation of 10 percent. Sensitivity can be improved by analyzing

liquid concentrations. Initial applications of this technique are determination of the uranium in natural waters and in experimental leach

solutions.

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2. Analytical Research Applied to Specific NBS Programs

a. Trace Element Profile in Auto Headlamp Glass

L. T. McClendon and T. E. Gills

In cooperation with the NBS Law Enforcement Standards Laboratory

(LESL) , the Activation Analysis Section has completed a program to

evaluate the feasibility of identifying glass from a common origin.

Automobile headlamp glass was chosen as a test case because automobile

headlamp glass fragments are frequently obtained as evidence specimens

in various kinds of criminal investigations, particularly from automobiles involved in hit-and-run accidents. Glass fragments from the

suspect's vehicle, when found at the crime scene, provide evidence to be

compared for simularities. Conventional criminalistic techniques, such

as the measurement of the refractive index of the glass fragments in

question, are quite helpful, however, more points of comparison are often necessary for positive identification.

Previous studies of trace elements in window glass have established

the potential value of multi-element analysis for the identification

and characterization of various glass types. However,- these studies were made without the advantages of the modern, sophisticated

analytical instruments available today. With these recent advances in

analytical instrumentation, greatly improved sensitivity and specificity

can now be obtained for multi-element analyses.

The technique used for this work, neutron activation analysis

coupled with high resolution gamma-ray spectroscopy, has been proven to

have several distinct advantages, including its excellent sensitivity

for many trace elements and the obtainable accuracy and precision (5-10%

overall) at the trace level. This technique also has the flexibility to

allow for multielement analysis of a sample and still preserve the

sample for future reference. In the case of criminalistic investigations,

preservation of the evidence for court examination is a desirable

feature.

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To assess the distribution of trace element^ in auto headlamp

glass, one hundred sixty-four (164) different fragments, representing

thirty-six (36) headlamps have been analyzed for 10-12 trace elements

using instrumental neutron activation analysis. The headlamps analyzed

were representative of the two major American manufacturers, Corning and

General Electric.

The data obtained on the auto headlamps analyzed indicate that:

(1) consistent analytical precison can be obtained on small headlamp

glass samples using the INAA technique; (2) auto headlamp glass manufactured by both Corning and General Electric is homogeneous for the

major constituent (Na) and relatively homogeneous for the trace elements;

(3) the trace element content of one headlamp vs any other has been

shown to differ appreciably under controlled experimental conditions,

demonstrating the feasibility of individualization of auto headlamps;

and (4) general trace element content of Corning manufactured headlamps

is not unique compared to those manufactured by General Electric,

indicating the probability of class characterization through a trace

element profile is relatively small.

An overall evaluation of the data obtained in this study indicated

the trace element profile of automobile headlamp glass fragments using

the neutron activation analysis technique could provide unambiguous

identification for forensic purposes. A manuscript for publication in

Analytical Chemistry, describing this study in' detail, is in preparation.

b. Assessment of Gunshot Residue Methodology

T. E. Gills, P. D. LaFleur, and D. A. Becker

The method of gunshot residue analysis can be a powerful tool in

helping to establish the innocence-or-guilt of an accused person. Ruch,

et. al . , demonstrated the practicality of using neutron activation to

detect such residue deposits, which are indicated by barium and antimony,

at very low concentrations. On numerous occasions law enforcement

agencies have introduced GSR test results in court as an aid in pros86
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ecution. Not only do prosecutors use it as an aid to convict or to

interrogate, but defense attorneys are finding it practical to use it to

exonerate a suspect.

While many methods can satisfy the sensitivity requirement for the

elements determined in gunshot residues, a relatively few have combined

both the sensitivity of a technique with a statistically- evaluated data

base so as to set up criteria for determining a handgun discharge.

Many laboratories are using only the quantification of Ba and Sb as valuable GSR information and are ignoring information on the population distributions of handgun firings and the ratios of Ba and Sb.

Because of these facts, the reliability of GSR tests has been seriously

questioned.

Recently, in support of the Law Enforcement Standards Laboratory

at NBS, the Activation Analysis Section has become involved in assessing

current GSR methodology. The main objective was to develop and/or

recommend a practical sampling and analysis procedure for gunshot

residue . tests which had been evaluated to give statistically reliable

results. With this objective in mind, the Activation Analysis Section

undertook a program to review the current analytical methodology,

improve it where possible and to provide an extensive data base on both

general population blank levels and post handgun firing levels of barium

and antimony.

At the onset of this work, consultations with many law enforcement

officials and visits to forensic laboratories were made to document

their experiences with GSR and to highlight the strengths and shortcomings of the GSR methodology. Following the review of current procedures, selected areas affecting the reliability of GSR results were researched. The areas that were studied are:

Analytical Methodology

Handgun Firings

Occupational Handblanks

87
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Persistence and Stability of Gunshot Residue

Data Evaluation

The data from both the handblank survey and the handgun firings were used in the formulation of a firing criterion. When the GSR

measurements were made, only the barium and antimony levels were logged.

Copper, though commonly found in each sample, was too ambiguous to be

used in any criterion formulation.

Even though there are large variations in the firing data,

correlation can be made between barium and antimony by using their

concentrations and their ratios. It should be restated that in any

criterion, all relevant information should be included or considered.

Therefore, upon this thesis we propose to separate the firing data from

the handblanks by setting up a frequency distribution relating con- centrations of barium and antimony, and their ratios, to average values

of each element and ratio found in a known set of firing distributions.

This frequency can be set up by the formula:

F B Sb

(Ba,Sb) = X

C + ( A A -

A B) 2

Constant = an empirically selected constant that

maximize F.

B = the average barium to antimony ratio of

each firing distribution, i.e., 22's, 38's,

and 45' s. A = the barium and antimony ratio of an individual

firing.

B, Sb. . _ , A, A = respective concentration of barium and antimony

found in each firing.

with such calculations the ratios and concentration of barium and

antimony in actual firings are mathematically related to the average

ratio of barium and antimony in known firing distributions. Using these
NON-RRD NBS PROGRAMS

values, a distinct demarcation can often be observed between handblanks

and firings.

A manuscript containing the complete results of this study is in

preparation for the Journal of Forensic Science.

Two Projects have been completed in the area of water analyses.

These programs were funded and coordinated by the Office of Air and

Water Measurement.

c. Evaluation of Lyophilization for the Preconcentration

of Natural Water Samples

S. H. Harrison and P. D. LaFleur

Neutron Activation Analysis is presently used to analyze various

aquatic samples, however, the applicability of the technique to the

water matrix is hindered by two main factors: very low concentrations

of the elements of interest, and interferences from more concentrated

dissolved species.

Except for Na and CI in sea water, most natural waters contain

such low concentrations of most elements that few can be accurately

determined directly on bulk water samples by completely instrumental

techniques. The sensitivity of analysis can be greatly improved by

concentration of the dissolved species from the water into a different medium, or removal of water to leave a residue of the dissolved material that can be irradiated in a small sample container.

The latter approach was used by Mamuro et al. who evaporated the

water prior to irradiation. Since evaporation is generally a slow

process carried out in the open, it is subject to possible difficulties.

These difficulties include contamination by fallout particles from

laboratory atmosphere, dissolution of ions from container surfaces, and

loss of volatile species if performed at an elevated temperature.

Other workers have devised chemical separation methods for removal

89
NON-RRD NBS PROGRAMS

of specific elements from water, but these could not be applied to the

multielement instrumental NAA.

The work presented here deals with the preconcentration of water

by freeze drying using a method which virtually eliminates sample

contamination and trace element losses. Freeze drying is a method

commonly used for drying biological tissues in which trace element may

be bound organically. Also, it has been used for drying natural water

although without associated evaluations of the technique. However,

questions may be raised regarding the suitability of this method of

concentration that point to the possibility of losses of volatile

elements during the drying process and the ability to transfer quantitatively the dry residue from the freeze drying container to an irradiation container.

The first question arises because it is known that some trace

elements can exist in chemical forms that have significant vapor pressures at room temperature, with respect to that of water. When a sample

containing such compounds is placed in a vacuum system for a extended

length of time, trace element losses from the sample will most likely

occur. A major object of this work was to determine if there are significant losses of various elements in water when the water is subjected

to freeze drying.

To evaluate this question, known quantities of radioactive tracers

for 21 elements (including many known to be volatile) were added to

water, the solutions freeze dried and the tracer residues counted (table

1) . The results confirm that at least 95% of all but the most volatile

elements studied (Hg and I) were retained in the residue. The second

question, concerning sample transfer, was eliminated by designing a freeze drying container which also would serve as an irradiation and

counting container. The material chosen was liner polyethylene film

(Phillips Petroleum's Marlex) . The preconcentration and containment

system has been used successfully in our laboratory for the INAA of

river and estuarine water samples.

90
NON-RRD NBS PROGRAMS

The results of a typical analysis of dissolved species in water by

INAA following the described preconcentration procedure appear in table

2. This sample was taken from the Back River, just east of Baltimore,

Maryland. The ratio of trace element content in the sample to the

average trace element content in a polyethylene bag is sufficiently high

for most elements to result in reliable data.

A complete report of this work has been published in Analytical

Chemistry, 47, 1685 (1975).

91
NON-RRD NBS PROGRAMS

Table 1. Trace Element Retention Yields for Freeze-Drying Water

ement Isotope n Range, % Average, %

kt a Na 2h Ka 3 95.8-99.4 97.4 ± 1.8

Sc 46 Sc 5 91.5-103.3 97.9 ± 4.3

V

4 8V 2 100.0-100.8 100.4 ± 0.3

Cr bl Cr 4 94.3-98.5 95.9 ± 2.0

Fe 59 Fe 1 101.1

Co 60 Co 6 94.2-100.0 97.5 ± 2.2

Zn 65 Zn 1 102.6

As 74As 6 94.8-98.5 96.3 ± 1.8

Se 75 Se 6 93.5-100.0 96.2 ± 1.8

Br

a 82 Br 3 97.4-100.8 99.3 ± 1.7

Rb 86 Rb 4 99.4-103.6 101.2 ± 1.8

Sr 85 Sr 1 . . . 101

Ag 10imAg 1 98.1

Cd 109Cd 4 94.9-113 102 ± 8

Sb 124 Sb 6 96.7-99.7 98.6 ± 1.1

I 126 T 3 46.9-88.0 68 ± 21

Cs 137 Cs 1 99.3

Ba 13 3 Ba 6 91.8-100.6 97.7 ± 3.0

Au 195Au 4 92.1-95.0 94.0 ± 1.3

Hg 2 3 Hg 4 50.1-71.0 61 ± 9

Tb 16 Tb 1 98.7

Ce 141 Ce 2 97.5-99.1 98.3 ± 1.1

Tracer solution used was not acidified.

92
NON-RRD NBS PROGRAMS

Table 2. Results of INAA of Freeze Dried Residue of

Back River Sample

Element residue, ng/g of water ng in Poly bag

Eu 0.24

Sc 0.31

Th 0.089

Cr 5.4

Fe 530

Co 1.2

Sr 440

Ag 0.24

Zn 12.3

Ba <35

Sb 0.64

Se 0.33

Na

a 0.53 mg/g

Cl

a 0.84 mg/g

Mn

a 0.23 yg/g

The results for Na , CI and Mn were obtained on a liquid

sample and are presented for informational purposes only.

d. A Study to Define the Long Term Stability of A Mixed

Trace Element Water Standard

H. L. Rook, J. R. Moody, P. J. Paulsen, and T. C. Rains

The National Bureau of Standards is currently developing a mixed

trace element in water standard. The standard will contain approximately

ten trace heavy metals of ecological significance, with emphasis on elements needing improved analytical accuracy at or below the part-permillion (10 6 g/g) concentration level.

93

>20

118

2.5

0.51

30

10

>300

7.7

3.2

6.0

10
NON-RRD NBS PROGRAMS

As a preliminary requirement to the production and certification

of this standard, a study into the long-term stability of the component

trace elements at the sub part-per-million level has been carried out.

Initial studies were conducted with radioactive tracers to determine

possible losses to container walls and interelement interactions

which might result in losses. Following this initial study, a more

comprehensive investigation was carried out using simultaneous analyses

by three trace analytical techniques; atomic absorption, neutron activation, and isotope dilution mass spectroscopy. This second study was

designed to indicate any problems of concentration elevation due to

reagent blanks or leaching of trace elements of the earlier tracer

study.

e. Stability Study

A solution containing ten selected heavy metals was prepared by

dissolving weighed amounts of the pure elements in acid and diluting to

the desired concentration. The elements included in the standard were:

As, Be, Cd, Cr, Cu, Hg, Mn, Pb, Se, and Zn. They were all at or below

the yg/g concentration level. The solution was stabilized with nitric

acid brought to a final concentration of 0.5 M plus approximately 10

ng/g gold ion as the chloride. The gold was added to stabilize mercury

as demonstrated in previous work on trace mercury standards

.

Storage containers used in this study were thoroughly cleaned by

prolonged leaching with dilute nitric and hydrochloric acids. All

containers were emptied of the acid mixture, rinsed, and filled with

ultra pure water until used.

Five radioactive tracers were added to one liter of the stock

solution and stored in one of the precleaned Teflon bottles. The

elemental concentration of the tracer solutions were low enough so as not to effect the total elemental concentrations of the stock solution.

The time stability study was carried out by withdrawing one ml of the

solution at intermittent intervals over an eight month period. The

activity of the individual tracers at a given time was decay corrected

94
NON-RRD NBS PROGRAMS

and compared to the activity at the start of the experiment. None of

the metals, except possibly cadmium, gave any indication of loss during

storage (table 1). This study, although indicating negligible loss on storage, yielded no information as to potential blank problems, either

from reagents or from wall leaching. To study these problems areas and

to determine if there would be any analytical problems during the

certification phase of this work, actual analyses of the original

solution was carried out.

Table 1. Tracer Study on Long-Term Stability

Relative Concentration

Time in Days

Isotope 7 14 22 35 79 94 255

73As 1.00 1.04 — 0.96 1.03 1.08 .97

75 Se 1.01 1.04 0.99 1.01 1.00 1.00 .98

2 3 Hg 1.00 1.03 1.03 1.01 0.98 1.00 1.03

10g Cd 1.00 — 0.97 = 98 0.94 0.97 0.98

65 Zn 0.98 1.00 1.00 1.00 1.00 1.02 1.02

The initial analyses for all elements were taken within one week

of preparation of the standard. With the exception of arsenic, the

results were in good agreement with the calculated concentration.

Arsenic was 30 percent low and may have been lost during the preparation

of the sample.

The standard was again sampled and analyzed after 17 weeks of

storage in the containers. The results show that no significant loss of

any element occurred over this time interval. For some elements there were apparent increases in concentration when stored in Teflon but these were within analytical uncertainties.

95
NON-RRD NBS PROGRAMS

Bibliography

1. H. L. Rook and J. R. Moody, "Stabilization and

Determination of Nanogram Quantities of Mercury in

Water", Proceedings Nuclear Methods in Environmental

Research. University of Missouri-Columbia (July 1974)

(in press)

.

f. A Study of the Location and Turnover of Lithium and Biogenic

Amines in Brain Using the Nuclear Track Technique

B. S. Carpenter, D. Samuel, and I. Wasserman

Experiments are being conducted to further the understanding of

the neurochemistry of affective disorders by mapping the distribution

and turnover of biogenic amines (dopamine, norepinphrine and serotonin)

using the nuclear track technique.

The method is based on the fact that Li-6 and 0-17 among the few

stable isotopes that emit alpha particles when irradiated with thermal

neutrons. The amount and location of these isotopes in any biological

material can be determined by the alpha particle tracks left in a solid

state track recorder.

In preliminary work, it has been shown that the distribution of Li

in the brain and the location of biogenic amines formed by inhaling

0-17 can be determined.

Further work is being conducted to elucidate the action of Li

which is an effective and highly specific drug for the treatment of

mania and depression. The development of 0-17 labelling of biogenic

amines will be used to assess their regional turnover and other parameters in response to psychoactive drugs and behaviorial situations.

96
NON-RRD NBS PROGRAMS

3. Analytical Support for the SRM Program

The Activation Analysis Section has devoted approximately one third of the entire years' effort in support of the Standard Reference

Materials (SRM's) program. This effort has been divided between the

improvement of analytical methodology, some of which were summarized in

the first part of this report, and the actual coordination and analytical

certification of new materials.

In total, the Activation Analysis Section has reported 811 elemental

concentrations in 24 different Standard Reference Materials. These

analyses encompassed a variety of materials including iron, copper,

coal, water, fuel oil, glasses, urine, sediment, cholesterol, serum, and

five different botanical materials. For a number of the above mentioned

SRM's the Activation Analysis Section was responsible for a large

fraction of the trace element certification data.

4. Service Analyses

In addition to the analyses conducted in support of the Standard

Reference Materials; a large number of additonal analyses were made on materials from Service Programs. These include both cooperative analyses,

where the analysis was made on samples of mutual interest to NBS and some other organization, and also service analyses, where the technical

expertise of the Activation Analysis Section was required by NBS or another Government agency.

During the past year the Activation Analysis Section has had a total of eight different cooperative or service analytical projects,

resulting in the analysis of 74 different samples for a total of 335

determinations. These projects were in conjunction with three other NBS

groups, and a number of other Government agencies, including the National

Institutes of Health, the National Institute of Occupational Safety and

Health, the Environmental Protection Agency, the Department of Agriculture,

Naval Research Laboratory, and the Department of Transportation.

97
NON-RRD-NBS PROGRAMS

1. W. D. Kinard, D. A. Becker, and P. D. LaFleur "The

Determination of Indium and Copper in SRM High Purity

Gold Wire by Neutron Activation Analysis", in

Activation Analysis Section : Summary of Activities , edited by P. D. LaFleur and D. A. Becker, NBS Tech.

Note 548 (1970)p. 66-69.

2. D. A. Becker, "Trace Analysis for Platinum in Glasses

by Neutron Activation", Anal. Chem. Acta, 6JL, 1 (1972).

3. K. S. Park, R. Gijbels, and J. Hoste, "Neutron Activation

Analysis of Palladium, Platinum and Rhodium in Lead

Foam", J. Radioanalybioal Chem. 3 5_, 31 (1970).

NEUTRON REACTION RATES AND STANDARD NEUTRON FIELDS

J. Grundl, D. Gilliam, V. Spiegel, Jr., H. Heaton

I. Schroder, R. Dallatore

(Neutron Standards Section)

The activities of the Neutron Reacton Rates Program are centered

around the reactor thermal column facility. Important efforts this past

year included preparation of NBS double fission chambers for experiments

undertaken at NBS and at U.S. and foreign laboratories, performing

fissionable deposit mass assays, and investigations of fission chamber

performance for operation in hostile neutron environments. Interaction

with power reactor technology in this program is via participation in

the Interlaboratory LMFBR Reaction Rate Program (ILRR) . This interlaboratory program of measurement assurance for breeder reactor fuels

and materials dosimetry presented a compendium of its activities and

results this year in the February, 1975, issue of Nuclear Technology

which devoted the entire issue to the ILLR program. Absolute fission cross section measurements with a californium 252 fission neutron source made

98
NON-RRD NBS PROGRAMS

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use of fissionable deposit mass intercomparisons in the reactor thermal

beam as did the program of international comparison of absolute fission

rates measurement scales.

1. Mass Assay of NBS Fissionable Deposits

At the present time the National Bureau of Standards set of fissionable deposits includes five major isotopes, Pu-239, U-235, U-238, Np-237,

and U-233. The deposits have been fabricated at four different laboratories and represent more than a dozen different batches of fissionable

materials. Mass assignments for the fissionable deposits are based on interrelated measurements methods: (1) quantitative deposition from

prepared solutions of known concentrations; (2) absolute alpha counting

combined with isotopic assay from mass spectrometry and alpha decay

constants from the literature; (3) relative fission fragment emission

rates from the deposits determined with both thermal and fast neutrons.

When completed each fissionable deposit will have associated with it an absolute alpha disintegration rate and a fission rate ratio which will

establish the mass relative to one or more reference fissionable deposits

of the same type. The reference deposits are kept aside from the normal

course of programmatic fission measurements.

The components of fissionable deposit mass assay just described

have been discussed in previous NBSR Annual Summaries. During this year

a primary effort was undertaken to assign critically evaluated masses

to the reference deposits. The final mass assignments are based on at

least two independent methods of mass determination for each isotope

except depleted uranium. The results are shown in table 1 where the

assigned mass for each reference deposit is the weighted average of all

of the independent values given. With reference deposit masses established masses for the working fissionable deposits are obtained on the

basis of comparison fission counting and relative alpha counting.

Standard deviations for these mass transfer determinations carried out

at the NBSR thermal column are better than ±1/2 percent.

101
NON-RRD NBS PROGRAMS

2. The NBS Double Fission Ionization Chamber

The NBS double fission chamber is a high resolution double ionization

chamber of minimized volume and mass designed as a probe to measure absolute

fission rates in a wide variety of neutron environments. The assembled fission chamber and enlarged cross section of the dual chamber head are shown in

figure 1. The chamber contains two independent fast ionization chambers

the fissionable deposits, on either platinum or quartz and positioned bach

to back, serve as the common grounded electrode between the chambers.

In order to reduce neutron absorption and scattering effects, the electrodes and scattering elements are made of aluminum and the insulators

are made of a hydrogen-free polymer. The mass of each piece has been

kept to a minimum and there exists calculated geometry factors for each

piece which make it possible to estimate scattering effects in both beam ard

isotropic neutron fields. The double chamber is designed to allow easy

Table 2. Average Fission Cross-Section Ratios for CFRMF

I Observed

Observed Comjputed t

— ,238TT , .— ,235TTN a

f

( U)/a ( U)

- ,237M N ,- ,238TT . a

f

( Np)/a

f

( U)

a

f

( 239Pu)/a

f

( 235

U)

0.0485±1.4% 1.138

7.34 ±2.3%

1.145 ±1.5%

0.975

1.034

and repeated access for exchange of fissionable deposits. The pulse

processing electronics system which has been designed for flexible use

out in the field is shown in figure 2. Typical pulse height distributions

for uranium deposits of different thicknesses are shown in figure 3.

The pulse height distribution displays three distinct features: (1) a very broad peak with a sharp initial rise; (2) the p.h.d. valley in

which the integral discriminators are set; and (3) the rising tail near

102
NON-RRD NBS PROGRAMS

ACTIVE-FILTER

SHAPING

AMPLIFIER

I.5us \—

\FVVHM/

FISSION

CHAMBER!

CHARGE

SENSITIVE

PREAMPLIFIER

T z^A—

SCALER 1 COUNT = S L

VL DISCRIMINATOR

VL =0.27x VpEAK FOR U DEPOSITS

VL

= 0.36 x VpEAK FOR Pu DEPOSITS

II II SCALER 2

COUNT = S u

Vu DISCRIMINATOR

Va

= 0.54 x VPEAK

II II 1 SCALER 3

COUNT = S GC

SINGLE CHANNEL ANALYZER

WINDOW FROM Vu TO VGC

1 TIMER - CON TROL MULTICHANNEL

ANALYZER

TFi cr-rvDcr i r

Figure 2. Each side of the dual fission chamber is monitored independently by a triple-sealer pulse-processing system as shown

here. The integral discriminator counts, S^ and Sy, are the

primary (redundant) counting data. The SCA count S GC provides

a sensitive gain check; Vq

c = 1.37 V .

zero pulse height due to alpha activity and electronic noise, etc. The

correction to zero pulse height (etz) taken from the scaler data (1-STT /S ) has been found to decrease nearly linearly with decreasing deposit

thickness. This dependence, established down to very thin deposits

(y5 yg/cm ) is taken presently as proper evidence that the chamber

itself operates with essentially 100% detection efficiency. The reproducibility of the (1-S /S ) data under normal conditions is such that this

quantity provides a reliable indicator of the advent of any significant

electronic noise above S . The peak-to-valley ratios of the pulse

u

2 height distribution as given in figure 3 vary from 34 for a 196 Ug/cm

o deposit to 240 for a 4 yg/cm deposit. Corresponding to this resolution,

the counting efficiency of this chamber is highly stable even for large

gain shifts. A gain shift of 10% for example leads to a change of less

than 0.2% in the count rate (Sy) for deposits of up to 200 ug/cm thickness

103
NON-RRD NBS PROGRAMS

3. Absolute Fission Rate Measurements in CFRMF

The capability to measure absolute fission rates per nucleus at a remote laboratory site (the Coupled Fast Reactivity Measurement Facility;

CFRMF, at Aerojet Nuclear Corporation) has been established with the NBS

double fission chamber to a precision of better than ±1 percent. This

precision was sustained for a period of more than two years. During

this period of time the NBS double fission chamber was used to establish

absolute fission rates and to monitor a series of high level radiations

designed to calibrate fission activation detectors used for breeder

reactor fuels and materials dosimetry. The array of reference and

I I I I I I

l Milll| i

<

CC -5 U_ 10

TT

o HEAVY DEPOSIT

l96 M g/cm 2

• LIGHT DEPOSIT .

-EXTRAPOLATED

FISSION PULSE

DISTRIBUTIONS

I

I compresse:

SCALE (1/5]

I 20 VL 4 ,60 80 ,,140 200 30C 400

PULSE HEIGHT (CHANNELS)

Figure 3. Typical pulse-height distributions for uranium fission counts

The pulse-height distribution of valid fission pulses is

assumed to be flat in the range QfVfVjj; the total count is

derived from an integral discriminator count above VL on the

basis of the flat extrapolation assumption.

104
NON-RRD NBS PROGRAMS

working fissionable deposits included four isotopes: Pu-239, U-235, U-238,

and Np-237. Isotopic masses for the fissionable deposits were determined

in work at the NBSR thermal column as were important performance

characteristics for the fission chamber. Absolute accuracy for the

fission rates per nucleus measured in CFRMF are in the range of ±1.3% to

±2.5% and are dominated by uncertainties in the fissionable deposit

masses. These uncertainties were reduced by nearly a factor of two

since the CFRMF measurements began. Efforts to improve the mass assignments to near ±1% and to achieve added confidence by means of interlaboratory comparisons is an on-going project at NBS.

Fission cross section ratios provide a useful characterization of

the high energy components of neutron spectra like that of CFRMF. Since

the array of measured U-235 and U-238 fission rate ratios does not vary

by more than ±0.3% during the CFRMF measurements, very consistent final

values for these fission ratios are obtainable. Fission rate ratios

obtained in CFRMF are listed in table 2 and compared there with predicted

values based on neutron transport computations. The observed spectral

— ?3S — ? "^ S index j ( U)/o f ( U) characterizes the spectrum as more energetic than

computed. This is a commonly observed feature of fast neutron

spectra although it is not always observed to this extent in a spectrum

as degraded energy as CFRMF. Of equal interest is the rather good

agreement between the observed and the computed Pu-239, and U-235 fission

cross section ratios in table 2. If the ENDF/B-IV fission cross sections

are as good as ±5% as is often presumed, this agreement indicates that

the low energy component of CFRMF is closer to the results of computation than the results predicted by measured neutron spectra.

4. Thermal Fission Yields for Long Lived Fission Products

The experimental program of measuring thermal fission yields at the

NBS thermal column was described briefly in the previous NBSR Annual

105
NON-RRD NBS PROGRAMS

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NON-RRD NBS PROGRAMS

Summary. Data reduction and reports of these measurements are now

complete and a more complete summary of the measurement and its outcome

are now possible.

Three U-235 fission activation foils were irradiated separately

in the NBSR thermal column. During each irradiation specific fission

counts (fission/mg U-235) were determined by observing fissions from a calibrated depleted uranium deposit inside of an NBS fission chamber.

The fission activation foil in which the fission yield was to be measured

also was positioned inside of the chamber adjacent to the calibrated

deposit—see figure 4. Corrections relating the absolute fission count

obtained from the deposit to the specific fission count attributed to

the activation foil were computed and tested experimentally at NBS.

Specific fission counts in the neighborhood of about 1 x 10 fissions/

milligram U-235 were observed with an accuracy of ±1.7% to ±2.0%. The

dominating errors were the uncertainty in the mass of the reference U-235

deposit (1.2%), the uncertainty in the correction for the U-238 fission

in the working deposit (0.63% to 1.25%), and the uncertainty in the

calibration of the working deposit mass relative to the reference deposit

mass (0.72%). The total number of fissions in the activation foils was inferred from the measured specific fission counts and the activation

foil masses as reported by the supplier, The Isotope Target Laboratory

at ORNL.

Four participants in the ILRR Interlaboratory Program for Fuels and

Materials Dosimetry- - AUG, ANL, ARHCO, HEDL—took part in the determination

of the fission product activities by means of Ge(Li) gamma spectrometry.

The gamma counting results furnished by these laboratories after the

radiations have been combined with the fission counting data and the

foil mass data to obtain absolute thermal fission yields. The thermal

fission yield values obtained in these experiments both absolute, and

relative to Ba-140, agree well with the ENDF/B-IV tabulation in most

cases. The full table of results will not be presented here. Of equal

importance and a prime motivation for these experiments is to examine

107
NON-RRD NBS PROGRAMS

the question of fission yield energy dependence. In table 3 fission

yields obtained from the CFRMF measurements described above are compared

to the yield measurements obtained in the NBS thermal column. The fast/

thermal yield presented in this table do not agree very well with the

corresponding ENDF/B-IV ratios. Discrepancies range from 6 to 10 percent.

These discrepancies are not considered final because of certain drawbacks

in the thermal column fission yield experiments, but as they stand,

they are of considerable significance for understanding fission rate

measurements with activation dosimeters in fast reactor fuels tests in

this country.

5. International Comparison of Absolute Fission Rate Measurement Scales

Interlaboratory comparisons have been made during the past two years

of techniques that are currently being applied to the measurement of fission

rates and U-238 capture rates in a number of zero-power fast critical as- semblies related to LMFBR development programs. This effort involved the

exposure of absolute fission chambers from four separate laboratories to

the central neutron field in the Sigma Sigma Facility operated by the

CEN/SCK laboratory at Mol Belgium. Uncertainties in measured reaction

rates estimated by each laboratory relative to flux monitors at Sigma

Sigma are between ±1.5% and ±3.5%. Uncertainties for the NBS fission

chamber measurements at Sigma Sigma are in the range of ±1.6% for U-235,

U-238 and Pu-239; Np-237 uncertainties are ±1.9%. Discounting the

deposit mass error fission rate uncertainties for the Sigma Sigma measurements are between ±0.3% and ±0.6%. This last uncertainty is taken as a mark of success for remote field operation with the NBS fission chambers.

Interlaboratory agreement for U-235, U-238 and Pu-239 fission rates is

in the range ±0.5% to ±1.3%. Important discrepancies appear in the U-238

capture measurement and further interlaboratory efforts which will include

NBS, are under consideration for solving this basic problem for fast

breeder reactors.

108
NON-RRD NBS PROGRAMS

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NON-RRD NBS PRQGRAMS

6. Fission Cross Sections for Californium-252 Fission Neutrons

Intense Cf-252 spontaneous fission sources with known source strength

and of small volume and mass are attractive neutron sources for performing

absolute cross section measurements in elementary geometry. An absolute

determination of the U-235 cross section for Cf-252 fission neutrons has

been carried out with two NBS double fission chambers in compensated beam

geometry, the NBS set of reference and working double fission deposits,

and the NBS manganese sulfate bath facility. In parallel measurements

the ratios of fission cross sections of U-238, Pu-239 and Np-237 were

determined for Cf-252 fission neutrons relative to the U-235 absolute

measurements. These measurements provide normalization data for certain

differential fission cross sections and for the general validation of

evaluated energy dependent fission cross sections. The U-235 (n,f)

absolute experiment is directly applicable for cross section normalization

because fission shape uncertainties are of little significance. For any

credible departure of fission shape from its normal Maxwellian description, the value of the U-235 (n,f) cross section will not vary by

more than 0.4 percent. The experiments are simple and direct and hence

the major effort is directed at understanding error components. A list of

these error sources, corrections applied, and the percent uncertainty

attached to them are listed in table 4 for the absolute U-235 cross section measurement.

The final Cf-252 fission-spectrum-averaged U-235 fission cross section obtained in these experiments is 1204±29 mb at a confidence

level of 67 percent. A computed cross section value using ENDF/B-IV

U-235 fission cross sections and a Californium fission spectrum evaluated

by NBS is 1245 mb. The disagreement of 3.4% is a significant one and an effort will be undertaken to reduce the error in the observed value which

as with other measurements of this kind at NBS is dominated by the fissionable deposit mass uncertainty. It is at the NBS reactor thermal column

that much of the effort to improve fissionable deposit mass assay is

centered. Results for the fission cross section ratio measurements is

110
NON-RRD NBS PROGRAMS

235 Table 4. Error Components for ' U Fission Cross Section Measurement

1 ^Percent

1 Correction Error

Mass of Fission Deposit Pairs

i

(381.4 and 934.0 yg/cm2

) 1.3

Source Strength

(4 x 109 n/s) 1.2

Fission in other isotopes 0.9987 0.1

Geometrical Measurements

Fissionable Deposit Separation 0.6

Finite deposit diameter 1.0075 0.1

Source not at mid-point 1.001 0.2

Undetected Fission Fragments

(light deposit)

Extrapolation to zero pulse height 1.0090 0.5

Absorption in fissionable deposit 1.0132 0.3

Neutron Scattering

Total room return 0.9955 0.2

Source capsule 0.9940 0.8

Fission chamber 0.9888 0.4

Support structures 0.9945 0.5

Platinum deposit backing 0.9870 0.8

Total Error 2.4%

235

"Error in U(n,f) cross section due to uncertainty in the listed

component

.

Ill
NON-RRD NBS PROGRAMS

252

Table 5. Fission Cross Section Ratios for Cf

Fission-Spectrum Neutrons

Nuclides ov Ratio Total

Uncertainty

Mass Assay

Uncertainty

o Ratio

ENDF/

B-IV

Discrepancy

Present Work/

ENDF

Present Work

238

u/

235

u 0.266 ±1.7% ± 1 . 5% 0.251 6.0%

239

Pu/

235

U 1.500 ±1.6% ±1.4% 1.440 4.2%

23 V235

u 1.105 ±2.2% ±2.1%

i

1.080 2.3%

shown in table 5. There is a considerable discrepancy with the predictions of ENDF/B/IV; in particular, the Pu-239 to U-235 ratio, discrepancy

is 4.2% well outside of the errors of the fission spectrum measurement

and also outside of the presumed accuracy of the ENDF/B-IV file.

The discrepancy of the U-238/U-235 ratio in table 5 has been

observed in other fission spectrum measurements but never with the

clarity that has become possible with the advent of intense and isolated

Californium fission sources. The 6% discrepancy is related to the discrepancy of 14% for the same cross section ratio observed in the CFRMF

reactor measurements discussed above. These types of disagreements

are of interest for reactor physics and for reactor fuels and materials

dosimetry. Once again in order for these validation measurements to

achieve maximum impact it will be necessary to reduce mass assay un- certainties to below the values listed in table 1. In this particular

case where mass assay of the threshold fission isotopes (U-238 and

Np-237) are involved, reference and working fissionable deposits will be

exposed not only in thermal beams, but also in the cavity fission source facility which operates at the center of the thermal column. This

facility provides high-quality fission neutron fluxes above one MeV at

c i. in 9 nn 10 , 2 an intensity of between 10 to 10 n/cm -s.

112
NON-RRD NBS PROGRAMS

ANGULAR ANISOTROPY IN THE

6

Li(n,a)

3

f-l REACTION AT 25 keV

I. G. Schroder

and

E. D. McGarry

(Harry Diamond Laboratories, Adelphi, MD)

and

G. de Leeuw-Gierts and S. de Leeuw

(SCK-CEN Mol, Belgium)

f< ? The angular anisotropy in the Li(n,a) H reaction at 25 keV has

been measured in two sets of experiments performed at an iron-filtered

beam facility (99% of the flux at 25 keV) at the NBS reactor. First,

— ? f> a surface-barrier detector coated with 80 yg*cm of LiF (front face) was used as a 2tt detector. This detector was placed in four different

angular positions with respect to the neutron beam: front face at 90°

and 45° to the beam; back face at 90° and 45° to the beam. The pulseheight distributions of both the H-3 and He-4 were recorded for these

four positions yielding a forward-to-backward asymmetry of 1.59±0.11 in

the center-of-mass system. A second detector was placed coaxially with

the first (at 90° to the beam) and in such a way as to subtend a 45° cone. Coincidence measurements, that simultaneously recorded the

distributions in both detectors, yielded an asymmetry in the backwardto-forward 45° cone of 1.80±0.06 in the center-of-mass system. The

existence of such a large anisotropy at this low energy and the possibility

of similar behavior at still lower energies (i.e., 1 - 2 keV) should

result from s-p wave interference. This would give rise to a constant

anisotropy that is experimentally masked by the 1/v behavior of the

isotropic s-s interference terms at lower energies

.

113
NON-RRD NBS PROGRAMS

PRECISION MEASUREMENT OF THE WAVELENGTHS OF NUCLEAR GAMMA LINES

AND THE COMPTON WAVELENGTH OF THE ELECTRON

R. D. Deslattes, E. G. Kessler, W. C. Sauder and A. Henins

(Optical Physics Division)

In this experiment the wavelengths of nuclear y-lines and the

Compton wavelength of the electron are measured in terms of the wavelengths of a molecularly stabilized visible laser. The y-rays are diffracted by Ge or Si crystals which are located on a two axis Laue

case transmission crystal spectrometer. The two quantities which must

be accurately measured are the crystal spacing and diffraction angles.

The lattice spacing of the crystals is determined by establishing

the lattice spacing of a standard silicon crystal by simultaneous optical

and x-ray interferometry of a common baseline. Next, a non-dispersive

transfer from the standard silicon crystal to a sample of the crystals

used in the experiment is performed.

The crystal diffraction angles are measured on the two axis spectrometer which is equipped with a modified Michelson angle interferometer.

In this modification crystal rotation is encoded as polarization rotation

with a 90° polarization charge corresponding to 70 milli arc sec. Faraday

modulators and step driven Glan-Thompson analysers permit servo-control to

about 0.3 milli arc sec or better. This angle measuring system was completely designed, constructed, and tested within the past nine months.

The interferometers were calibrated by summing to closure measurements of the interfacial angles of a 72-sided optical polygon. The

provisional analysis of the calibration data has provided an interferometer constant accurate to 0.4 ppm.

A 40 Ci Au-198 y~ray source was prepared by the irradiation of a Au

foil in the NBS reactor. The wavelength of the 412 keV 198-Au line was measured with a result of 3.010766 pm (±2 ppm) being obtained. By

applying the voltage-wavelength conversion factor to this number, the

2 energy was found to be 411.8062 keV (±3.3 ppm).

114
NON-RRD NBS PROGRAMS

We hope to lower the uncertainty to less than 1 ppm in future y-ray

measurements by using stronger sources to obtain better statistics, by

improving the Soller collimators so that the vertical divergence correc- tion is better known, and by making the crystal spacing transfer more

accurately.

1. R. D. Deslattes and A. Henins, Phys. Rev. Lett. 31, 972 (1973).

2. R. D. Deslattes, E. G. Kessler, W. C. Sauder, and A. Henins,

Proceedings of the Fifth International Conference on Atomic

Masses and Fundamental Constants (Plenum Press, NY) to be

published

.

MEASUREMENT OF THE RATIO OF THE ABSORPTION CROSS SECTIONS

FOR MANGANESE AND HYDROGEN

J. R. Smith

(Aerojet Nuclear Company, Idaho Falls, Idaho)

and

S. D. Reeder

(Allied Chemical Company, Idaho Falls, Idaho)

and

B. M. Coursey

(Applied Radiation Division)

and

V. Spiegel

(Nuclear Sciences Division)

The manganese bath technique is perhaps the foremost method

presently available for determining absolute yields of neutron

sources. The principal of the method is quite simple. Neutrons from

the source are completely absorbed in a surrounding solution of

Mn SO. dissolved in water. The absorbed neutrons induce in the solution

4 an activity of Mn-56 proportional to the strength of the source. There are a number of corrections that must be applied to the

Mn-56 activity observed before the source strength is deduced. The

present study is concerned primarily with just one of these: the

115
NON-RRD NBS PROGRAMS

fact that not all of the absorbed neutrons produde Mn-56 . Even in a saturated solution the fraction absorbed in manganese is less than

60%. In commonly used concentrations, the fraction ranges between

35% and 50%, with most of the remainder absorbed in hydrogen. The

accuracy with which the fractional absorption in manganese can be

determined, therefore, depends upon the accuracy with which the ratio

of the absorption cross sections of manganese and hydrogen can be

established

.

Axton " developed the technique of varying the concentration of

the manganese bath and extrapolating measurements to zero hydrogen

content . From such measurements the source strength can be derived

without reference to separately measured cross sections for hydrogen

and manganese. However, the hydrogen-to-manganese cross section ratio

can be derived from the concentration-dependent manganese bath

activation data. It is determined from the ratio of the slope to the

intercept of the linear curve obtained from plotting the reciprocal

of the Mn-56 activity observed against the hydrogen-to-manganese

atomic density of the solution.

2 DeVolpi has also made concentration-dependent measurements,

obtaining hydrogen-to-manganese cross section ratios differing from

the Axton data by about 1.4%. This does not necessarily imply a corresponding error in source strength measurements, but it suggests

the existence of unresolved problems in the systematics of the

measurement. For example, Axton and DeVolpi disagree on the values of some of the manganese bath corrections, which must be applied to

linearize the relationship between inverse Mn-56 activity and the

H/Mn numerical ratio. The principal corrections in question are those

for leakage, manganese resonance absorption, and high energy parasitic

absorption in oxygen and sulfur. Because of the implications for

Cf-252 v measurements by the manganese bath technique, it was thought

important to make a concentration-dependence study for a neutron

source for which these effects are negligible. Such a source is a

116
NON-RRD NBS PROGRAMS

neutron beam well below the manganese resonance energies and the

"1 /" TO OO <jn thresholds of the 0(n,a) C and S(n,p) P reactions.

At the National Bureau of Standards Reactor an experiment is in

progress to determine the hydrogen-to-manganese cross section ratio in

a manganese bath using a low energy neutron beam and the concentration

variation technique. A Bragg beam of approximately 0.02 eV is obtained

by reflection of the reactor beam from a crystal of pyrolytic graphite.

Neutrons coming from higher order Bragg reflections or from potential

scattering in the crystal are suppressed by filters of pyrolytic

graphite and quartz crystals. The Bragg beam first passes through a manganese-aluminum monitor foil and then into the bath. The ratio of

solution to monitor activity provides a measure of neutron-induced

activity independent of reactor fluctuations.

The concentration of the solution is varied over a range from

30 to 530 grams of MnSO, per liter of solution. Because preliminary

investigations indicated that the disagreement between Axton and

DeVolpi might be traceable to concentration determinations, the

concentration is being measured three ways: by evaporation of a sample of solution and weighing of the residual salt, by measuring

the density and comparing with a density-vs .-concentration curve, and

by titration of a sample of solution with EDTA.

The efficiency of counting Mn-56 activity in a solution varies

with the concentration. Therefore, counter calibrations are carried

out at each concentration. Calibrations are performed by counting in

the manganese bath counting system an aliquot of Mn-56 sample whose

absolute disintegration rate has been determined in the NBS ion chamber,

Measurements have thus far been made at four concentrations. At

least that many additional points will be required for a reliable

determination of the hydrogen-to-manganese cross section ratio.

1. E. J. Axton et al . , J. Nucl . Energy Parts A/B 19_, 409 (1965)

2„ A. DeVolpi and K. G. Porges, Metrologia 5_, 128 (1969).

117
E. Summary of Reactor Hperations

Although the reactor was shut down from August 9, 1974 to

January 20, 1975, for the installation of three new heat exchangers

the operating productivity remained very high for the period of

time available for operations (78% on-line time) . A summary of the

overall operating statistics for this and previous years is presented

in the following table.

NBSR Operating Summary

1972 1973 1974 1975

Reactor Operations to date, MWh 175,000

Reactor Operations for year, MWh 51,000

Hours Reactor Critical

Number of Days at 10 MW

On-line Time at 10 MW

Number of fuel elements used

Average U-235 Burnup

Number of Refueling Operations

Number of Unscheduled Shutdowns

Number of Irradiations

Number of Visitors

5,000 229 ,000 290 ,000 328 ; ,000

1,000 67 ,000 61 ,000 38 : ,000

5,200 7 ,000 6 ,600 3 ,900

214 279 254 157

58% 77% 70% 43%

26 28 24 16

45% 52% 54% 53%

6 7 6 4

11 14 6

4,000 4 ,300 3 ,000 1.,550

3,400 3,,000 5,,000 3,,000

118
SUMMARY OF REACTOR OPERATIONS

REPLACEMENT OF THE NBSR MAIN HEAT EXCHANGER

J. H. Nicklas

The main B^O to process water heat exchanger made of aluminum had

failures of the "U" tubes. The primary cause of failure was fretting of

the "U" tubes against the baffles due to vibration.

It was decided that the replacement of the heat exchanger would

include a spare because of cost advantages and the desirability of

having a spare. The heat exchangers are made of stainless steel, type

304 L; low carbon chosen to eliminate carbide precipitation during

welding. All tubes are welded to the solid stainless steel tubesheet in

addition to being rolled into grooves of the tubesheet holes. Secondary

inlet and outlet nozzles are attached to domes on the shell which reduces

the impingement velocity of the fluid on the "U" tubes. Three inspection

ports have been installed on each shell to observe corrosion product

buildup and possible fouling from the chemical inhibitors used in the

system.

The heat exchangers were installed through a floor opening in the

experimental floor by professional riggers. After appropriate piping

was welded and assembled to the heat exchangers, pressure and flow tests were run separately on the primary and secondary systems.

At about one-half the rated full flow in the secondary, a rattling

sound was heard in the shell in the area of the "U" tubes. The last

baffles in the heat exchanger next to the "U" tubes contain a window for

flow and therefore contain "U" tubes of a greater unsupported length

than tubes not in the window. A hole was cut in the shell in close

proximity to the baffle window. The tubes in the baffle windows were

"laced" with flattened tubes running between the tube rows and placed on both sides of the baffle. After closing the shell, flow testing at

approximately 115% of rated flow was conducted with no rattling of the

tubes being heard.

119
SUMMARY. OF REACTOR OPERATIONS

When flow tests were conducted on the primary system a scraping

sound was heard in the bonnet of one heat exchanger but not in the

other. Investigations through a port hole of the bonnet showed that a gasket between the tubesheet and divider plate had partially slipped

out. It was determined that the divider plate had deflected sufficiently

to allow the gasket to come free. Two heavy stainless steel bars were

bolted to both sides of the divider plate to limit the deflection after

the gasket was reinstalled in its groove. Flow tests were conducted at

approximately 150% of design flow with no noise being heard in the

bonnets.

Each heat exchanger has operated satisfactorily for several months.

One heat exchanger is being dried out for storage as a spare unit.

120
F. Service Programs

Service and irradiation programs were curtailed this year because

the reactor was shut down for the installation of new heat exchangers.

In all, approximately 1550 irradiations were performed this year.

Again, the irradiations covered a wide variety of programs. Highlights

are presented in the following sections.

ACTIVATION ANALYSIS PROGRAM OF THE

FOOD AND DRUG ADMINISTRATION AT THE NBSR

J. T. Tanner and M. H. Friedman

(Food and Drug Administration, Washington, B.C.)

The activation analysis unit of The Food and Drug Administration

(FDA) is located at the National Bureau of Standards in the Reactor

Building. Neutron activation analysis (NAA) has been used by the FDA

for trace metal analysis of foods, drugs, hair, laundry aids, and

cosmetics . The service of this group is available to anyone within

the FDA both in the headquarters laboratory and in the field. The

project described below accounts for the main effort of NAA at the FDA.

1. General

The "Total Diet" program of the Food and Drug Administration

(FDA) is a continuing market basket study in which 117 food items are collected, prepared in a "table-ready" fashion, and composited into 12

commodity groups for analysis for selected metals, pesticides, and

certain industrial chemicals to determine the average daily intake of

these contaminants in the diet. The sampling is intended to represent

the 2-week diet of a 15- to 20-year old male in each of four regions

of the country in which the samples are collected: Northeastern,

Southeastern, Central, and Western. The details of the selection,

collection, preparation, and compositing of the samples are described

elsewhere. The different commodity groups are: Dairy products; meat,

fish and poultry; grain and cereal products; potatoes; leafy vegetables

legume vegetables; root vegetables; garden fruits; oils and fats;

beverages ; and sugars

.

121
SERVICE PROGRAMS

The FDA Kansas City District Laboratory has the main responsibility

for analysis of the Total Diet samples. In addition to pesticides,

i these composits are routinely analyzed for Hg, As, Se, Pb , Cd, Zn, Ca,

Fe, P, and I. At various times the Neutron Activation Analysis (NAA)

group of the FDA has aided the Kansas City Laboratory when improved limit

of detection was required. Mercury was determined in Total Diet composites

2 for one year by NAA. The results have been reported elsewhere.

During the past year the FDA has been testing and evaluating NAA

methodology for the surveillance of a number of trace elements in foods.

Elements which are of interest to FDA include Fe, Co, Sb , Rb , Cs , Zn,

Se , and Ca. Some of these elements produce long lived radionuclides on neutron irradiation and therefore offer the possibility of determination

by instrumental NAA (INAA) . These include Fe, Co, Rb , Cs , Zn, Se, Cr,

Sc, Hg, and Ag. Others are short lived and may also be determined by

INAA. These are K,, Mg, Na, Dy, Mn, Ni , V, Al, In, CI, Br, I, Ca, and

As. While it may not be possible or practicable to determine all of

these elements by INAA at least some of them possibly can be determined

(Fe, Co, Zn, Sb , Rb , Se, K, Mg, Na, Mn, Al , and Br) and upper limits

established for other elements. The purpose will be to provide

additional information for elements not determined by the Kansas City

Laboratory, provide an interlaboratory comparison within FDA, and

provide greater sensitivity for some elements where only upper limits

are now obtained by Kansas City.

Our initial survey consists of a one year Total Diet sampling.

Based on the results obtained, the time required per analysis, and the

total work load, the use of INAA for routine surveillance will be

evaluated

.

In addition to INAA, group separation methodology for multielement analysis is being developed for FDA by researchers at the

Washington State University. This will provide improved sensitivities

for some elements.

122
SERVICE PROGRAMS

2. Analysis of Elements with Long Half-Lives

The elements which are considered for analysis using a long

irradiation (4-6 hours) and a long decay time (2-4 weeks) are Fe-59

(45d), Co-60 (5.3 y) , Sb-124 (60d) , Rb-86 (19d) , Cs-134 (2.1y),

Zn-65 (245d), Se-75 (120d) , Cr-51 (28d), Sc-45 (84d) , Hg-203 (47d)

,

and Ag-110 (253d).

Total diet samples and standards were irradiated together for

4 to 6 hours in one of two reactor positions (flux of 10 or 6 x lO-^

n/cm -sec) and allowed to decay for between one to two months before

analysis. For Co, Fe, Sb , Zn and Se the detection limit was considered

adequate and no chemical separation was necessary; however, for mercury

2 this was not the case and a chemical separation was used. Radionuclides

and energies of the gamma-rays which were used for the analyses are Co-60 (1173.1, 1332.4 keV) , Fe-59 (1098.6, 1291.5), Sb-124 (1690.7),

Zn-65 (1115.4), Se-75 (136.0, 264.6) and Hg-203 (279.1). The National

Bureau of Standards Orchard Leaves (SRM 1571) are used as a standard for

Fe and Zn and NBS Bovine Liver (SRM 1577) was used for the remaining

elements as a standard. The samples and standards were counted using

an automatic data acquisition system and reduced on a UNIVAC 1108

computer using the program MTELMR. The results are given in Table 1.

The remaining elements (Rb-86, Cs-134, Cr-51, Sc-46, and Ag-110) were below the detection limit. As a further extension to this part

of the work, upper limits will be calculated for these elements, thus

giving partial information regarding their concentration and/or occurrence

in foods.

3. Analysis of Elements With Short Half-Lives

The elements which are used for analysis using a short irradiation

time (15 sec) and a short decay time (60 sec) are K-42 (12. 4h),

Mg-27 (9.5m), Na-24 (15h) , Dy-165 (2 . 3h) , Mn-56 (2.6H), Ni-65 (2.6h),

V-52 (3.8m), Al-28 (2.3m), In-116m (54m), Cl-38 (37.3m), Br-82 (36h)

,

1-128 (25m), As-76 (26h) , and Ca-49 (8.7m). The most likely elements

which could occur in foods at detectable levels are K, Mg, Na, Mn, Al,

123
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125
SERVICE PROGRAMS

Ci, Ca, and Br, Upper limits could be calculated for the other elements

as described in the preceding section. MBS Standards are used as element

standards

.

Radionuclides and energies of the gamma-rays which were used

for the analyses are K-42 (1524.7), Mg-27 (1014), Na-24 (1368, 2754),

Mn-56 (1811), Al-28 (1778), 01-38 (1642,7, 2167.6), Ca-49 (3084.4),

and 0u-66 (10 3?. 2). The data are summarized in Table i,

Duggan, R. F.. s and F. J. McFairlancl, Pesticides Monitoring Journal ., Vol. 1, pp 1-5 (1967).

2. Tanner, .1, T„, * n d M. S, Forbes, Anal, Chi.m. Acta 74_, 17-2.1 (1975).

ATF'S FORENSIC ACTIVATION ANALYSIS PROGRAM

C. M. Hoffman

(U.S. Treasury Department, Washington, DC)

Neutron activation analysis continues to be valuable as a primary

or supplementary analytical tool in our Forensic Laboratory. The

ability to analyze minute amounts of evidentiary material non-destructively is a distinct asset where the material must be preserved for

courtroom presentation.

During FY75, 257 case related samples were analyzed by NAA. These

samples consisted of gunshot residue, hair, bullet leads, paints, glass

and soil.

Paint samples collected from 26 major U.S. manufacturers have been

collected and will be analyzed for their trace element profiles. These

data will be used to establish the probabilities necessary for comparing

forensic specimens.

NAA has been used to examine writing inks for the presence of tab

elements put in by the manufacturer who wishes to identify his product

and its production date. This work will be continued in FY76.

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THE USE OF ACTIVATION ANALYSIS IN SCIENTIFIC CRIME DETECTION

BY THE FEDERAL BUREAU OF INVESTIGATION

J. F. Gallagher

(Federal Bureau of Investigation, Washington, DC)

The Neutron Activation Analysis (NAA) Group in the FBI Laboratory

has continued to use NAA as one method of elemental analysis in materials

as diverse as lead, copper, steel, biologicals, aluminum, gunshot

residues and synthetic fibers.

For many of the elements of interest in aiding in the characterization of materials involved in criminal matters, there is no method

of analysis with better precision and accuracy.

Additionally, the common problems of contamination and limited

sample size can be overcome. During FY 1975, three Special Agents assigned to the NAA Group

testified on numerous occasions in local, state and federal courts.

LUNAR SAMPLE ANALYSIS FOR 17 TRACE ELEMENTS

E. Anders

(University of Chicago, Chicago, IL)

During the last year we have analyzed 12 samples for 17 trace

elements (Ag, Au, Bi, Br, Cd, Cs, Ge, Ir, Ni, Rb, Re, Sb, Se, Te, Tl, U

and Zn) by radiochemical neutron activation using the NBS reactor.

Abundances of siderophile elements (Au, Ge, Ir, Ni, Re, Sb) in Apollo

17 boulders and breccias show that rocks of the 2.3 km high massifs contain a uniform type of meteoritic materials. This appears to be derived

from the planetesimal whose impact excavated the Serenitatis basin about

4 billion years ago (Higuchi and Morgan, 1975; James et at. , 1975). A

light grey boulder from near the crest of the massif is the one major

exception. It contains an unusual meteorite type and appears to pre-date

the Serenitatis impact (Morgan et al. , 1975a)

.

A unique eucritic meteorite, Ibitira, resembles lunar basalts in

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several respects; vesicularity , mineral assemblage and texture; bulk

composition. Volatile trace elements are much higher in Ibitira, however,

and reflect differences in composition between the Moon and the eucrite

parent body (Morgan et at., in preparation, 1975a).

1. H. Higuchi and J. W. Morgan, Ancient meteoritic components in Apollo 17

boulders, Proa. Lunar Sci. Conf. 6th3 (1975) in press.

2. 0. B. James, A. Brecher, D. P. Blanchard, J. W. Jacobs, J. C. Brannon,

R. L. Korotev, L. A. Haskin, H. Higuchi, J. W. Morgan, E. Anders,

L. T. Silver, K. Marti, D. Braddy, I. D. Hutcheon, T. Kirsten, J. F. Kerridge, I. R. Kaplan, C. T. Pillinger, and L. R. Gardiner, Proc. Lunar

Sci. Conf. 6th, (1975) in press.

3. J. W. Morgan, H. Higuchi, and E. Anders, Meteoritic material in a boulder

from the Apollo 17 site, The Moon, (1975a) in press.

4. J. W. Morgan, H. Higuchi, and E. Anders, Unbrecciated eucrites, in

preparation (1975b).

TRACE ELEMENTS IN THE ENVIRONMENT AND

RADIOACTIVE DECAY STUDIES

W. H. Zoller, G. E. Gordon and W. B. Walters

(University of Maryland, College Park, Maryland)

Our group has made extensive use of the NBSR for the irradiation

of numerous samples for trace-element analysis using instrumental

neutron activation analysis (INAA) . We have had our computer-based

Northern Scientific analyzer system and two Ge(Li) y~ray detectors

at the Reactor for periods of several weeks during the last year to

count short-lived radioactive products. Most of the other samples

are returned to the University of Maryland for counting when longer

half-lived isotopes are involved.

During the last year numerous samples from our studies of

coal- and oil-fired power plants have been analyzed for trace-element

species. The projects involving the coal-fueled power plant emissions

have shown that a fair amount of elemental fractionation does occur during the combustion process. The volatile elements Se, As, Pb , Sb

,

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and several others are redistributed onto the smaller sized particles.

The enrichments relative to background values are not sufficient to

account for observed atmospheric concentrations. Work on municipal

incinerators has indicated that this is a very important source of many

toxic trace metals in urban air. The particle size distribution also

shows that the particles produced are in the resperable size range.

Samples from the South Pole and Iceland have been analyzed, and

papers published on these results. More work is envisioned on the

Antarctic samples throughout the next year to further substantiate

our findings to date. Our results from activation analysis are described

in more detail in progress reports to the NSF RANN Project (G. E. Gordon

et_ al_. , Study of the Emissions from Major Air Pollution Sources,

June, 1974, available from National Technical Information Service,

No. PB242581/AS, $10/copy, $2.25 for microfiche; the 1975 report now

in preparation will also be available through NTIS)

.

The radioactive decay of two nuclides have been studied

using sources produced at the NBSR during the past year. The

angular correlations of the Rh-105 y

- rays produced in the decay

of 4.4-hr Ru-105 have been studied and low-lying 1/2 and 3/2

states identified. The decay of a new isomer 42-min Eu-154m has

also been studied and coincidences among its y~rays determined.

Analysis of the coincidence spectra of the decay of 70-sec Se-83m

has continued.

TRACE ELEMENTS IN OCEANIC FLOOR ROCKS

F. A. Frey

(Massachusetts Institute of Technology, Cambridge, MA)

Our use of the NBS reactor is for neutron activation analysis of

geological samples. The analytical techniques have been documented by

Gordon et al. (1968) and Hertogen and Gijbels (1971).

During the last year, our research has been concentrated on determination of trace element abundances in basaltic rocks drilled in the

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ocean floor during the Deep Sea Drilling Project. These elements are typically abundant in the parts per million range in such rocks, and

neutron activation is one of the few techniques enabling accurate analysis. The ocean floor is composed of basalts whose trace element composition is unlike similar appearing rocks on continents and oceanic islands,

Because many trace element abundances, e.g., rare-earth elements are very

sensitive, indicators of the processes involved during magma formation, we can utilize a knowledge of trace element abundances in ocean floor

basalts to learn about the nature of their source region in the upper

mantle, and the mechanisms controlling the generation of magma within

the earth.

G. E. Gordon, K. Randle, G. G. Goles, J. B. Corliss, M. H. Beeson and

S. S. Oxley, Geoohim. Cosmoohim. Aota3 32, 369 (1968).

J. Hertogen and R. Gijbels, Anal. Chim. Acta, 56, 61-82 (1971).

CHEMICAL CHARACTERIZATION OF MARINE AEROSOLS

P. E. Wilkniss

(Naval Research Laboratory, Washington, DC)

Although the ocean is the largest natural source of aerosols

(mainly in the form of sea salts) , in certain regions the marine

atmosphere may contain orders of magnitude greater concentrations

of particulate material supplied by wind erosion of continents.

Quantification and chemical characterization of this material is

necessary to determine the atmospheric flux of various elements and

the relative influence of anthropogenic processes on these elemental

budgets. Since the transport of these continental particles (eolian

dust) can vary greatly in space and time, the presence or absence

of dust in the marine sedimentological record can also elucidate

past wind patterns and climatic conditions of the dust source regions.

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In this research, nearly one hundred eolian dust samples

collected in the atmosphere over widely scattered regions of the

Atlantic and Pacific oceans are being analyzed for several trace

constituents. The method involves the use of neutron activation

followed by gamma ray spectroscopy. Following a one hour irradiation

in the NBS reactor (RT-4) , samples are counted at NRL after 3 days

and 40 days decay. The elements readily identified by this procedure

include barium, cerium, cesium, chromium, cobalt, europium, hafnium,

iridium, iron, lathanum, lutetium, potassium, rubidium, samarium,

scandium, silver, sodium, tantalum, terbium and zinc. Concentrations

of these elements are being compared among dust samples from various

regions as well as with sediment samples from prospective source

areas on land

.

TRACE ELEMENT STUDIES OF SELECTED

BIOLOGICAL SPECIMEN

G. A. Ferguson

(Howard University, Washington, DC)

Abnormal concentrations of trace elements have been suspected

in the genesis of a number of cancers. Of special interest are the

preliminary data on the high concentration of zinc in cancer of the

prostate and pancreas. Neutron activation analysis (NAA) is being

used as one method to study the role of trace elements in carcinogenesis

This study is being undertaken at Howard University because of its

unique historical involvement with health problems of the U.S. black

population which shows a rapidly increasing mortality rate attributable

to cancer. Multielement assay, using the NAA technique, of the large number

of specimen required for a meaningful study of the role of trace

elements has begun with preliminary data now being analyzed. Initial

investigations will determine the distribution of zinc in the prostate

of normal and abnormal subjects.

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ACTIVATION ANALYSIS PROGRAM OF THE U.S. GEOLOGICAL SURVEY

J . J . Rowe

(U.S. Geological Survey, Reston, VA)

The U.S. Geological Survey is applying Neutron Activation Analysis

to the determination of trace concentrations of elements in geological

materials. The improved sensitivity of Activation Analysis, for some elements, supplements other analytical techniques in the analysis of

rocks, minerals and waters for geochemical studies related to ore formation, magmatic differentiation, alternation, hydrothermal transport,

energy reserves (coal, petroleum, geothermal and nuclear) and environmental problems.

The Radioactivation and Radiochemical Analysis project is developing

'a comprehensive instrument method, using sample changers and computer

data reduction to provide data on trace concentrations of Ba, Ce, Co, Cr,

Eu, Fe, Gd, Hf, Nd, Rb , Sb , Se, Ta, Th, Yb, Zn and Zr in igneous and

metamorphic rocks. Sulfide minerals have been analyzed for Mn, As, Sb

,

Se, Ag, Hg and Au using instrumentation and radiochemical methods. Lunar

samples have been analyzed for Al, V, Mn, Hf, and Ta. Thermal waters

have been analyzed for gold for the Heavy Metals Program and a comprehensive analytical program is planned for the study of Geothermal Energy.

132
6, Staff Roster

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133
STAFF ROSTER

Division 240.01

P. R. Cassidy

H. E. DeSpain

E. J. Embree

R. Henessain

J. J. Shubiak

F. Moore

Division 241.05

R. A. Dallatore

R. Flemming

D. Gilliam

H. T. Heaton

J. A. Grundl

I. G. Schroder

R. Schwartz

V. Spiegel

NON-RRD MBS STAFF LOCATED AT REACTOR

Division 310.08

B. J. Clipper

S. B. Carpenter

R. H. Filby

S. S. Fine

E. Garrigues

T. E. Gills

S. H. Harrison

R. M. Lindstrom

G. J. Lutz

L. T. McClendon

H. L. Rook

J. E. Suddueth

GUEST WORKERS AND COLLABORATORS

Division 213.04

D. G. Eitzen

Division 232.06

R. D. Deslattes

W. C. Sauder

E. G. Kessler

Division 242.02

F. J. Schima

Division 310.01

D. Sweger

Division 311.03

C. Han

Division 312.02

R. Reno

Division 311.05

L. W. Schroeder

R. M. Waterstrat

Division 313.03

R. S. Roth

Division 313.04

G. J. Rosasco

Division 313.06

A. B. Mighell

C . S . Brickencamp

134
STAFF ROSTER

Argonne National Laboratory

H. Flotow

N. Lapinski

C. Pellazari

D. L. Price

K. Reimann

K. Skold

Battelle, N.W.

W. Nicholson

Federal Bureau of Investigation

D. B. Davies

J. Gallagher

J. W. Kilty

G. P. Mahoney

E. Mitchell

J. P. Riley

Food and Drug Administration

M. Friedman

J. T. Tanner

Harry Diamond Laboratory

C. Heimbach

D. McGarry

National Institutes of Health

D. Davies

R. Frank

W. Hagins

W. Robinson

Naval Air Systems Command

S. Goldberg

Naval Surface Weapons Center

(Dahlgren Laboratory)

G. Blessing

Naval Surface Weapons Center

(White Oak Laboratory)

H. Alperin

P. Hesse

D. Polansky

J

.

J . Rhyne

R. H. Williams

Naval Research Laboratory

D. Forester

G. A. Ferguson

J. Karle

J. H. Konnert

P. E. Wilkniss

Oak Ridge National Laboratory

H. A. Mook

M. Mostoller

H. G. Smith

Picatinny Arsenal

C. S. Choi

H. J. Prask

M. K. Farr

S

.

Trevino

U.S. Geological Survey

P. Baedecker

J . J . Rowe

U.S. Postal Service

M. Beckman

G. R. Stangohr

J. Upton

U.S. Treasury Department

R. L. Brunelle

P. C. Buscemi

C. M. Hoffman

F. A. Lund gren

135
STAFF ROSTER

American University

R. Abbundi

R. A. Segnan

R. Simon

Carnegie Institute of Washington

L. W. Finger

Colorado State University

C. E. Patton

Howard University

G. A. Ferguson

University of Maryland

W. Articola

E. Bailey

R. Cahill

C. Choquette

W. Cunningham

E. Gladney

G. Gordon

R. Greenberg

S. Jackson

W. Maenhaut

E. Mroz

J. Ondov

E. Schneider

J. Small

W. Walters

W. Zoller

Massachusetts Institute of Technology

F. A. Frey

Reed College

W. Parker

U.S. Naval Academy

C. S. Schneider

University of Chicago

E. Anders

R. Ganapathy

J. Morgan

University of Delaware

F. Williams

University of Rhode Island

S. J. Pickart

The Ford Motor Company

S. A. Werner

Gamma Industries

D. Garrett

Idaho National Engineering

Laboratories

H. D. Reeder

J. R. Smith

Old Delft Corporation

D. Bracher

Thiokol Chemical Company

E. Magnusson

Union Carbide Corporation

T. Taylor

136
H. Publications

COLLABORATIVE PROGRAMS

BERGER, H., "Detection Systems for Neutron Radiography," Proc . Symposium

on Practical Applications of Neutron Radiography and Gauging,

National Bureau of Standards, Feb. 10-11, 1975, to be published.

BERGER, H., "An Evaluation of Radiography Paper for Thermal Neutron

Radiography," Transactions of the American Nuclear Society, 21 , pp. 148-149 (1975).

H. BERGER, "A Summary of the Conference on Emerging Techniques for

Nondestructive Field Testing - Opportunities for NDT in Transportation," Materials Evaluation, 33_, No. 7, pp. 189-191 (July 1975).

H. BERGER, "Radiographic Nondestructive Testing," Standardization News,

2, No. 3, pp. 21-29 (March 1975).

H. BERGER, "Summary of the American Nuclear Society Topical Meeting,

Nondestructive Testing in the Nuclear Power Industry," Nuclear News,

18, No. 1, pp. 68-74 (Jan. 1975).

BICKFORD, N. A. and RABY, T. M. , "Description of Pneumatic Facilities at

the NBSR," Transactions of the American Nuclear Society, Aug. 12-14,

1974, p. 88-89 (1974).

CARTER, R. S., "Standards at the NBS Reactor," Transactions of the American

Nuclear Society, August 12-14, 1974, p. 39-40 (1974).

CASELLA, R. C, ROWE , J. M. , and TREVINO , S. F. , "On Determining the

Number of Independent Real Parameters in the Phonon Dynamical

Matrix," submitted to Phys. Rev.

CASELLA, R. C, ROWE, J. M. , and TREVINO, S. F. , "On Determining the Number

of Independent Real Parameters in the Phonon Dynamical Matrix,"

Phys. Rev., in press.

CASELLA, R. C, "Algorithm for Computing the Number of Independent

Parameters in the Phonon Dynamical Matrix',' Phys. Rev. , 11B , 4795 (1975).

CHOI, C. S., SANTORO, A., and MARINKAS , P., "1 , 3,5-triaceta-2 ,4 ,6-

trihydra-s-triazine (TRAT)," Acta Cryst. , in press.

CHOI, C. S., SANTORO, A., AND ABEL, J. E., "The Crystal Structure of

3 , 7-diacetyl-l ,3,5, 7-tetraazabicyclo [3,3, 1 Jnonane (DAPT) ",

Acta Cryst. , B31 , in press.

137
PUBLICATIONS

CHOI, C. S., PRASK, H. J., and PRINCE, E., "Crystal Structure of NH CIO,

at 298, 78 and 10°K by Neutron Diffraction," J. Chem. Phys. ,61,

3523 (1974).

FINGER, L. W. and PRINCE, E., "A Fortran 10 Program for Structure Factor

Calculation and Least Squares Refinement of Crystal Structures,"

NBS Tech. Note 854 (1975).

FRIZZELL, 0. E., DARR, J. H., and RABY, T. M. , "Non-Contact Irradiated

Fuel-Plate Temperature Measurements at the NBSR," Transactions of

the American Nuclear Society, Aug. 12-14, 1974, pp. 79-80 (1974).

GRAHAM, C. D., JR., and RHYNE, J. J., Editors, "Magnetism and Magnetic

Materials, American Inst, of Phys. Conf. Proc. Series 24_, (1975).

MIGHELL, A. D., SANTORO, A., PRINCE, E., and REIMANN, C. W. , "Neutron

Diffraction Structure Determination of Dichlorotetrapyrazolecopper

(II), Cu(C H N ) CI " Acta Cryst. B31 , in press.

MIGHELL, A. D. and SANTORO, A., "Geometrical Ambiguities in the Indexing

of Powder Patterns," J. Appl. Cryst. 8, 372 (1975).

PICKART, S. J., RHYNE, J. J. and ALPERIN, H. A., "Critical Neutron

Scattering in Amorphous HoFe'' AIP Conf. Proc. _24 (1975).

PICKART, S. J., RHYNE, J. J., and ALPERIN, H. A., "Anomalous Small-Angle

Magnetic Scattering from Amorphous TbFe

? and YFe„," Phys. Rev.

Letters 33, 424 (1974)

.

RHYNE, J. J., PICKART, S. J. and ALPERIN, H. A., "Atomic Structure and

Magnetism in Amorphous Terbium-Iron," Proc. llth Rare Earth

Research Conf., p. 1020, (1974).

PRASK, H. J., RUSH, J. J. and TREVINO, S. F. , "Quasielastic Neutron

Scattering Studies of Ammonium-Ion Reorientation in Ammonium

Perchlorate," J. Chem. Phys. 62_, 4156 (1975).

PRINCE, E., "Dimethyl Sulfone Diimine, A Neutron Study," Acta Cryst.,

in press.

PRINCE, E., TREVINO, S. F. and FARR, M. K. , "A Refinement of the Structure

of Deuterium Peroxide," J. Chem. Phys., in press.

RHYNE, J. J., "Local Anistropy and Exchange Effects in Amorphous TbFe '' Proc. Conf. on Crystalline Electric Fields 3 Univ. of Montreal

Bulletin, (1975).

RHYNE, J. J., PRICE, D. L. and MOOK, H. A., "Inelastic Magnetic Scattering

from Amorphous TbFe " AIP Conf. Proc. 24_, (1975).

138
PUBLICATIONS

RHYNE, J. J., "A Part of the Birth and Evolution of Rare Earth

Magnetism," Proa. Eleventh Rare Earth Research Conference,

p. 247 (1974).

RHYNE, J. J., SCHELLENG, J. H., and KOON, N. C, "Anomalous

Magnetization of Amorphous TbFe , GcFe , GdFe and YFe ,"

Rhys. Rev. BIO , 4672 (1974).

ROSASCO, G. J. and PRASK, H. J., "Polarized Raman Study of Lattice

Modes in Ammonium Perchlorate at Low Temperature," Sol. St. Cornm. 16, 135 (1975).

ROTSCHILD, W. G., ROSASCO, G. J. and LIVINGSTON, R. C, "Dynamics of

Molecular Reorientation Motion and Vibrational Relaxation in

Liquid Chloroform," J. Chem. Rhys. 62_, 1253 (1975).

ROWE, J. M., RUSH, J. J., VAGELATOS , N. and PRICE, D. L., "Crystal

Dynamics of KCN and NaCN in the Disordered Cubic Phase,"

J. Chem. Rhys. 62_, 4551 (1975).

ROWE, J. M., NICKLOW, R. M., PRICE, D. L. and ZANIO, K. , "Lattice Dynamics

of Cadmium Telluride," Rhys. Rev. 10B, 671 (1974).

RUSH, J. J., ROWE, J. M. and VAGELATOS, N. , "The Acoustic Modes of the

Phonon Dispersion Relation of NbD Alloys," Rhys. Rev., in press.

RUSH, J. J., SMITH, H. G., MOSTOLLER, M. and FLOWTOW, H. E., "Lattice

Dynamics of a Single Crystal of PdD_ ,_," Rhys. Rev. Lett. 3_3_, 1297 (1974).

SANTORO, A., CHOI, C. S. and ABEL, J. E., "l,5-Diacetyl-3,7 dinitro1,3,5-tetrazacycloctane (DADN)," Acta Cryst. B31 (1975), in press.

SCHROEDER, L. W. , PRINCE, E. and DICKENS, B., "Hydrogen Bonding in

Ca(H PO ) HO as Determined by Neutron Diffraction," Acta Cryst.

B31, 9 (19757.

SHEN, T. Y., MITRA, S. S. (U. R. Is.), PRASK, H. and TREVINO, S. F.

,

"Order-Disorder Phenomenon in Sodium Nitrate Studied by Low

Frequency Raman Scattering," Rhys. Rev., in press.

VAGELATOS, N. , ROWE, J. M. and RUSH, J. J., "Lattice Dynamics of ND

4

I in the NaCl Phase (I) of ND.I at 296°K," Rhys. Rev., in press.

139
PUBLICATIONS

INDEPENDENT PROGRAMS

ARAS, N. K. and WALTERS, W. B. , "The Decay of 4.44-hr 105

Ru to Levels

of 105RH," Physical Review, Cll , 927 (1975).

DESLATTES, R. D. , KESSLER, E. G. , SAUDER, W. C. and HENINS , A., "Visible

to Gamma-Ray Wavelength Ratio," Atomic Masses and Fundamental Constants5

(Plenum Press, NY) to be published.

DUCE, R. A., HOFFMAN, G. L.-and ZOLLER, W. H. "Atmospheric Trace Elements

at Remote Northern and Southern Hemisphere Sites: Pollution or Natural?" Saienoe3 187, 59 (1975).

FABER, T. M. , RITTER, D. L. , WEINBERGER, M. A. BIERBOWER, G. , TANNER, J. T.,

FRIEDMAN, M. H. , CARTER, C. J., EARL, F. L. and VANLOON, E. J.,

"The Toxicity of Brominated Sesame Oil and Brominated Soybean Oil

in Miniature Swine," Toxicology , to be published.

FORESTER, D. W. , ABBUNDI, R. , SEGNAN, R. and SWEGER, D. , "Magnetic

Hyperfine Structure in Amorphous DyFe '' AIP Conference., Proceedings

Series XXIV, 115 (1974).

GANAPATHY, R. , MORGAN, J. W. , HIGUCHI , H. , ANDERS, E. and ANDERSON, A. T.

,

"Meteoric and Volatile Elements in Apollo 16 rocks and in separated

phases from 14306." Proc. Lunar Sci. Conf. 5th, 1659-83 (1974).

GORDON, G. E., ZOLLER, W. H. , GLADNEY, E. S. and GREENBERG, R. R. , "The

Use of Instrumental Nuclear Activation Analysis Methods in the Study

of Particles from Major Air Pollution Sources," Proceedings,

Second International Conference on Nuclear Methods in Environmental

Research, Univ. of Missouri, 1974 (in press).

GREENBERG, R. R. , ZOLLER, W. H. and GORDON, G. E. , "Municipal Incinerators:

Source of Toxic Elements on Urban Aerosols, submitted to Science.

JACKSON, S. V., WALTERS, W. B. and MEYER, R. A., "Decay of 30-hr TeTM

To Levels of 131 I, Phys. Rev. C9, 2379 (1974).

KEAYS, R. R., GANAPATHY, R. , LAUL, J. C. , KRAHENBUHL, U. and MORGAN, J. W.

"The Simultaneous Determination of 20 Trace Elements in Terrestial,

Lunar and Meteoric Material by Radiochemical Neutron Activation

Analysis," Anal. Chim. Acta, 77, 1-29 (1974).

KILTY, J. R. , "Activity After Shooting and Its Effect on the Retention

of Primer Residue," Journal of Forensic Sciences, 20.» No - 2 (1075).

KINARD, W. D and LUNDY, D. R. , "A Comparison of Neutron Activation

Analysis and Atomic Absorption Spectroscopy on Gunshot Residue,"

ACS Symposium Series #13, Forensic Science, 97-107 (1975).

140
PUBLICATIONS

MCGARRY, E. D. and SCHROEDER, I. G. , "A 25keV Neutron Beam Facility

at NBS," Proceedings, Conf. on Nuclear Cross Sections and Technology,

Washington, DC (March, 1975).

MORGAN, J. W. , GANAPATHY, R. and KRAHENBUHL, U. , "Meteoritic Trace

Elements in Lunar Rock 14321,184," Geochim. Cosmoehim. Acta 39,

261-264 (1975).

MORGAN, J. W. , GANAPATHY, R. , HIGUCHI, H. , KRAHENBUHL, U. and ANDERS, E.,

"Lunar Basins: Tentative Characterization of Projectiles, From

Meteoric Elements in Apollo 17 Boulders," Proa. Lunar Sci. Conf. 5th.

1703-36 (1974).

MROZ, E. T. and ZOLLER, W. H. , "Composition of Atmospheric Particulates

from the Eruption of Heimaey, Iceland," Science (in press).

ONDOV, J. M. , ZOLLER, W. H. , OLMEZ, I., ARAS , N. K. , GORDON, G. E.,

RANCITELLI, L. A., ABEL, K. H. , FILBY, R. H. , SHAH, K. R. and

RAGAINI, R. C. , "Element Concentrations in the National Bureau of

Standards Environmental Coal and Fly Ash Standard Reference Materials,"

Anal. Chem., 4_7, 1102-09 (1975).

ONDOV, J. M. , ZOLLER, W. H. , OLMEZ, I., ARAS, N. K. , GORDON, G. E.

,

RANCITELLI, L. A., ABEL, K. H. , FILBY, R. H. , SHAH, K. R. and

RAGAINI, R. C. , "Four-Laboratory Comparative Instrumental Nuclear

Analysis of the NBS Coal and Fly Ash Standards," Proceedings, the

7th Materials Research Symposium: Accuracy in Trace Analysis,

National Bureau of Standards, (1974) in press.

SCHNEIDER, C. S., "Coherent Nuclear Scattering Amplitudes of Germanium,

Copper and Oxygen for Thermal Neutrons," to be published.

SCHROEDER, I. G. , MCGARRY, E. D. , DE LEEUW-GIERTS and DE LEEUW, S.,

"Angular Anisotropy in the 6L.( n ,a)-*H Reaction at 25 keV,"

Proceedings, Conference on Nuclear Cross Sections and Technology,

Washington, DC (March, 1975).

SCHROEDER, I. G. , SCHWARTZ, R. B. and MCGARRY, E. D. , "The 2-keV

Filtered Beam Facility at the NBS Reactor," Proceedings, Conference

on Nuclear Cross Sections and Technology, Washington, DC (March, 1975).

SCHWARTZ, R. B. , MCGARRY, E. D. and SCHROEDER, I. G. , "Filtered Neutron

Beams at the National Bureau of Standards Reactor," EUROPHYSICS

Conf. on Nuclear Interactions at Medium and Low Energies, AERE,

Harwell, England (March 1975).

141
PUBLICATIONS

ZOLLER, W. H., GLADNEY, E. S. , GORDON, G. E. and J. J. BORS, "Emissions

of Trace Elements from Coal Fired Power Plants," Trace Substances in

Environmental Health - VIII , D. D. Hemphill, ed. (Univ. of

Missouri, Columbia, 1974) pp. 167-171.

142
NBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLIC ATION OK REPORT NO. NBS TN-89 6

2. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE 5. Publication Date January 1976

NBS Reactor: Summary of Activities , July 1974 to June 1975 6. Performing Organization Code

7. AUTHOR(S)

Robert S. Carter

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Proiect/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP) 13. Type of Report & Period Covered 7-1-74 to 6-30-75

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less tactual summary of most significant information. If document includes a significant bibliography or literature survey, mention it here.)

This report summarizes all those programs which depend on the

NBS reactor. It covers the period from July 1974 through June 1975.

The programs range from the use of neutron beams to study of the

structure and dynamics of materials through nuclear physics and

neutron standards to sample irradiations for activation analysis,

isotope production and radiation effects studies.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Activation analysis; crystal structure; diffraction; isotopes; molecular dynamics

neutron; nuclear reactor; radiation

18. AVAILABILITY [2E Unlimited

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